7
| ||||
---|---|---|---|---|
Cardinal | seven | |||
Ordinal | 7th (seventh) | |||
Numeral system | septenary | |||
Factorization | prime | |||
Prime | 4th | |||
Divisors | 1, 7 | |||
Greek numeral | Ζ´ | |||
Roman numeral | VII, vii | |||
Greek prefix | hepta-/hept- | |||
Latin prefix | septua- | |||
Binary | 1112 | |||
Ternary | 213 | |||
Senary | 116 | |||
Octal | 78 | |||
Duodecimal | 712 | |||
Hexadecimal | 716 | |||
Greek numeral | Z, ζ | |||
Amharic | ፯ | |||
Arabic, Kurdish, Persian | ٧ | |||
Sindhi, Urdu | ۷ | |||
Bengali | ৭ | |||
Chinese numeral | 七, 柒 | |||
Devanāgarī | ७ | |||
Telugu | ౭ | |||
Tamil | ௭ | |||
Hebrew | ז | |||
Khmer | ៧ | |||
Thai | ๗ | |||
Kannada | ೭ | |||
Malayalam | ൭ | |||
Armenian | Է | |||
Babylonian numeral | 𒐛 | |||
Egyptian hieroglyph | 𓐀 | |||
Morse code | _ _... |
7 (seven) is the natural number following 6 and preceding 8. It is a prime number.
7 is often considered lucky in Western culture, hence its common use in slot machines. Unlike Western culture, in Vietnamese culture, the number seven is sometimes considered unlucky.[citation needed]
Mathematics
[edit]- 7, the 4th prime number, is not only a Mersenne prime (since ) but also a double Mersenne prime since the exponent, 3, is itself a Mersenne prime.[1]
- 7 is also a Newman–Shanks–Williams prime,[2] a Woodall prime,[3] a factorial prime,[4] a lucky prime,[5] a happy number (happy prime),[6] and a safe prime (the only Mersenne safe prime).[7]
- Seven is the only prime number preceding a cube.
- Seven is the lowest natural number that cannot be represented as the sum of the squares of three integers. (See Lagrange's four-square theorem#Historical development.)
- In decimal representation, repeats six digits (as 0.142857).[8][9]
- A seven-sided shape is a heptagon.[10] The heptagon is the first regular polygon that cannot be directly constructed with compass and straightedge.[11]
- The opposite sides of a standard six-sided die always add to 7. When rolling two standard six-sided dice, seven is the most likely total, having a 6 in 36 (or 1/6) probability of being rolled.[12]
- 7 is the only natural number D for which the Diophantine equation has more than two solutions for n and x that are also natural numbers. The equation is known as the Ramanujan–Nagell equation.
- In catastrophe theory, there are seven fundamental types of catastrophes.[13]
- The Fano plane contains seven points and seven lines. This is related to other appearances of the number seven in relation to exceptional objects, like the fact that the octonions contain seven distinct square roots of , seven-dimensional vectors have a cross product, and the number of equiangular lines possible in seven-dimensional space is anomalously large.[14][15][16]
- The Millennium Prize Problems are seven problems in mathematics that were stated by the Clay Mathematics Institute in 2000.[17] Currently, six of the problems remain unsolved.[18]
Simple calculations
[edit]Multiplication | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 50 | 100 | 1000 |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
7 × x | 7 | 14 | 21 | 28 | 35 | 42 | 49 | 56 | 63 | 70 | 77 | 84 | 91 | 98 | 105 | 112 | 119 | 126 | 133 | 140 | 147 | 154 | 161 | 168 | 175 | 350 | 700 | 7000 |
Division | 1 | 2 | 3 | 4 | 5 | 6 |
---|---|---|---|---|---|---|
7 ÷ x | 7 | 3.5 | 2.3 | 1.75 | 1.4 | 1.16 |
x ÷ 7 | 0.142857 | 0.285714 | 0.428571 | 0.571428 | 0.714285 | 0.857142 |
Exponentiation | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
7x | 7 | 49 | 343 | 2401 | 16807 | 117649 | 823543 | 5764801 | 40353607 | 282475249 | 1977326743 | 13841287201 | 96889010407 |
x7 | 1 | 128 | 2187 | 16384 | 78125 | 279936 | 823543 | 2097152 | 4782969 | 10000000 | 19487171 | 35831808 | 62748517 |
Numeral shape
[edit]This section needs additional citations for verification. (May 2024) |
For early Brahmi numerals, 7 was written more or less in one stroke as a curve that looks like an uppercase ⟨J⟩ vertically inverted (ᒉ). The western Arab peoples' main contribution was to make the longer line diagonal rather than straight, though they showed some tendencies to making the digit more rectilinear. The eastern Arab peoples developed the digit from a form that looked something like 6 to one that looked like an uppercase V. Both modern Arab forms influenced the European form, a two-stroke form consisting of a horizontal upper stroke joined at its right to a stroke going down to the bottom left corner, a line that is slightly curved in some font variants. As is the case with the European digit, the Cham and Khmer digit for 7 also evolved to look like their digit 1, though in a different way, so they were also concerned with making their 7 more different. For the Khmer this often involved adding a horizontal line to the top of the digit.[19] This is analogous to the horizontal stroke through the middle that is sometimes used in handwriting in the Western world but which is almost never used in computer fonts. This horizontal stroke is, however, important to distinguish the glyph for seven from the glyph for one in writing that uses a long upstroke in the glyph for 1. In some Greek dialects of the early 12th century the longer line diagonal was drawn in a rather semicircular transverse line.
On seven-segment displays, 7 is the digit with the most common graphic variation (1, 6 and 9 also have variant glyphs). Most calculators use three line segments, but on Sharp, Casio, and a few other brands of calculators, 7 is written with four line segments because in Japan, Korea and Taiwan 7 is written with a "hook" on the left, as ① in the following illustration.
While the shape of the character for the digit 7 has an ascender in most modern typefaces, in typefaces with text figures the character usually has a descender (⁊), as, for example, in .
Most people in Continental Europe,[20] Indonesia,[citation needed] and some in Britain, Ireland, and Canada, as well as Latin America, write 7 with a line through the middle (7), sometimes with the top line crooked. The line through the middle is useful to clearly differentiate the digit from the digit one, as the two can appear similar when written in certain styles of handwriting. This form is used in official handwriting rules for primary school in Russia, Ukraine, Bulgaria, Poland, other Slavic countries,[21] France,[22] Italy, Belgium, the Netherlands, Finland,[23] Romania, Germany, Greece,[24] and Hungary.[citation needed]
In science
[edit]- Seven colors in a rainbow
- Seven continents
- Seven climes
- The neutral pH balance
- Number of notes in the diatonic scale of Western music
- Number of spots most commonly found on ladybugs
- Atomic number for nitrogen
- Number of diatomic molecules
- Seven basic crystal systems
In psychology
[edit]- Seven, plus or minus two as a model of working memory
- Seven psychological types called the Seven Rays in the teachings of Alice A. Bailey
- In Western culture, seven is consistently listed as people's favorite number[25][26]
- When guessing numbers 1–10, the number 7 is most likely to be picked[27]
- Seven-year itch, a term that suggests that happiness in a marriage declines after around seven years
Classical antiquity
[edit]The Pythagoreans invested particular numbers with unique spiritual properties. The number seven was considered to be particularly interesting because it consisted of the union of the physical (number 4) with the spiritual (number 3).[28] In Pythagorean numerology the number 7 means spirituality.
References from classical antiquity to the number seven include:
- Seven Classical planets and the derivative Seven Heavens
- Seven Wonders of the Ancient World
- Seven metals of antiquity
- Seven days in the week
- Seven Seas
- Seven Sages
- Seven champions that fought Thebes
- Seven hills of Rome and Seven Kings of Rome
- Seven Sisters, the daughters of Atlas also known as the Pleiades
Religion and mythology
[edit]Judaism
[edit]The number seven forms a widespread typological pattern within Hebrew scripture, including:
- Seven days (more precisely yom) of Creation, leading to the seventh day or Sabbath (Genesis 1)
- Seven-fold vengeance visited on upon Cain for the killing of Abel (Genesis 4:15)
- Seven pairs of every clean animal loaded onto the ark by Noah (Genesis 7:2)
- Seven years of plenty and seven years of famine in Pharaoh's dream (Genesis 41)
- Seventh son of Jacob, Gad, whose name means good luck (Genesis 46:16)
- Seven times bullock's blood is sprinkled before God (Leviticus 4:6)
- Seven nations God told the Israelites they would displace when they entered the land of Israel (Deuteronomy 7:1)
- Seven days (de jure, but de facto eight days) of the Passover feast (Exodus 13:3–10)
- Seven-branched candelabrum or Menorah (Exodus 25)
- Seven trumpets played by seven priests for seven days to bring down the walls of Jericho (Joshua 6:8)
- Seven things that are detestable to God (Proverbs 6:16–19)
- Seven Pillars of the House of Wisdom (Proverbs 9:1)
- Seven archangels in the deuterocanonical Book of Tobit (12:15)
References to the number seven in Jewish knowledge and practice include:
- Seven divisions of the weekly readings or aliyah of the Torah
- Seven aliyot on Shabbat
- Seven blessings recited under the chuppah during a Jewish wedding ceremony
- Seven days of festive meals for a Jewish bride and groom after their wedding, known as Sheva Berachot or Seven Blessings
- Seven Ushpizzin prayers to the Jewish patriarchs during the holiday of Sukkot
Christianity
[edit]Following the tradition of the Hebrew Bible, the New Testament likewise uses the number seven as part of a typological pattern:
- Seven loaves multiplied into seven basketfuls of surplus (Matthew 15:32–37)
- Seven demons were driven out of Mary Magdalene (Luke 8:2)
- Seven last sayings of Jesus on the cross
- Seven men of honest report, full of the Holy Ghost and wisdom (Acts 6:3)
- Seven Spirits of God, Seven Churches and Seven Seals in the Book of Revelation
References to the number seven in Christian knowledge and practice include:
- Seven Gifts of the Holy Spirit
- Seven Corporal Acts of Mercy and Seven Spiritual Acts of Mercy
- Seven deadly sins: lust, gluttony, greed, sloth, wrath, envy, and pride, and seven terraces of Mount Purgatory
- Seven Virtues: chastity, temperance, charity, diligence, kindness, patience, and humility
- Seven Joys and Seven Sorrows of the Virgin Mary
- Seven Sleepers of Christian myth
- Seven Sacraments in the Catholic Church (though some traditions assign a different number)
Islam
[edit]References to the number seven in Islamic knowledge and practice include:
- Seven ayat in Surah al-Fatiha, the first chapter of the holy Qur'an
- Seven circumambulations of Muslim pilgrims around the Kaaba in Mecca during the Hajj and the Umrah
- Seven walks between Al-Safa and Al-Marwah performed Muslim pilgrims during the Hajj and the Umrah
- Seven doors to hell (for heaven the number of doors is eight)
- Seven heavens (plural of sky) mentioned in Qur'an 65:12
- Night Journey to the Seventh Heaven, (reported ascension to heaven to meet God) Isra' and Mi'raj in Surah Al-Isra'.
- Seventh day naming ceremony held for babies
- Seven enunciators of divine revelation (nāṭiqs) according to the celebrated Fatimid Ismaili dignitary Nasir Khusraw[29]
- Circle Seven Koran, the holy scripture of the Moorish Science Temple of America
- Seven earth as mentioned in the Quran[clarification needed]
- Seven children of Muhammad
- Seven years of abundance and seven of drought in Egypt during the time of Yusuf (Joseph) as mentioned in the Quran.[30]
Hinduism
[edit]References to the number seven in Hindu knowledge and practice include:
- Seven worlds in the universe and seven seas in the world in Hindu cosmology
- Seven sages or Saptarishi and their seven wives or Sapta Matrka in Hinduism
- Seven Chakras in eastern philosophy
- Seven stars in a constellation called "Saptharishi Mandalam" in Indian astronomy
- Seven promises, or Saptapadi, and seven circumambulations around a fire at Hindu weddings
- Seven virgin goddesses or Saptha Kannimar worshipped in temples in Tamil Nadu, India[31][32]
- Seven hills at Tirumala known as Yedu Kondalavadu in Telugu, or ezhu malaiyan in Tamil, meaning "Sevenhills God"
- Seven steps taken by the Buddha at birth
- Seven divine ancestresses of humankind in Khasi mythology
- Seven octets or Saptak Swaras in Indian Music as the basis for Ragas compositions
- Seven Social Sins listed by Mahatma Gandhi
Eastern tradition
[edit]Other references to the number seven in Eastern traditions include:
- Seven Lucky Gods or gods of good fortune in Japanese mythology
- Seven-Branched Sword in Japanese mythology
- Seven Sages of the Bamboo Grove in China
- Seven minor symbols of yang in Taoist yin-yang
Other references
[edit]Other references to the number seven in traditions from around the world include:
- The number seven had mystical and religious significance in Mesopotamian culture by the 22nd century BCE at the latest. This was likely because in the Sumerian sexagesimal number system, dividing by seven was the first division which resulted in infinitely repeating fractions.[33]
- Seven palms in an Egyptian Sacred Cubit
- Seven ranks in Mithraism
- Seven hills of Istanbul
- Seven islands of Atlantis
- Seven Cherokee clans
- Seven lives of cats in Iran and German and Romance language-speaking cultures[34]
- Seven fingers on each hand, seven toes on each foot and seven pupils in each eye of the Irish epic hero Cúchulainn
- Seventh sons will be werewolves in Galician folklore, or the son of a woman and a werewolf in other European folklores
- Seventh sons of a seventh son will be magicians with special powers of healing and clairvoyance in some cultures, or vampires in others
- Seven prominent legendary monsters in Guaraní mythology
- Seven gateways traversed by Inanna during her descent into the underworld
- Seven Wise Masters, a cycle of medieval stories
- Seven sister goddesses or fates in Baltic mythology called the Deivės Valdytojos.[35]
- Seven legendary Cities of Gold, such as Cibola, that the Spanish thought existed in South America
- Seven years spent by Thomas the Rhymer in the faerie kingdom in the eponymous British folk tale
- Seven-year cycle in which the Queen of the Fairies pays a tithe to Hell (or possibly Hel) in the tale of Tam Lin
- Seven Valleys, a text by the Prophet-Founder Bahá'u'lláh in the Bahá'í faith
- Seven superuniverses in the cosmology of Urantia[36]
- Seven, the sacred number of Yemaya[37]
- Seven holes representing eyes (سبع عيون) in an Assyrian evil eye bead – though occasionally two, and sometimes nine [38]
See also
[edit]- Diatonic scale (7 notes)
- Seven colors in the rainbow
- Seven continents
- Seven liberal arts
- Seven Wonders of the Ancient World
- Seven days of the Week
- Septenary (numeral system)
- Year Seven (School)
- Se7en (disambiguation)
- Sevens (disambiguation)
- One-seventh area triangle
- Z with stroke (Ƶ)
- List of highways numbered 7
Notes
[edit]- ^ Weisstein, Eric W. "Double Mersenne Number". mathworld.wolfram.com. Retrieved 2020-08-06.
- ^ "Sloane's A088165 : NSW primes". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-01.
- ^ "Sloane's A050918 : Woodall primes". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-01.
- ^ "Sloane's A088054 : Factorial primes". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-01.
- ^ "Sloane's A031157 : Numbers that are both lucky and prime". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-01.
- ^ "Sloane's A035497 : Happy primes". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-01.
- ^ "Sloane's A003173 : Heegner numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-01.
- ^ Wells, D. (1987). The Penguin Dictionary of Curious and Interesting Numbers. London: Penguin Books. pp. 171–174. ISBN 0-14-008029-5. OCLC 39262447. S2CID 118329153.
- ^ Sloane, N. J. A. (ed.). "Sequence A060283 (Periodic part of decimal expansion of reciprocal of n-th prime (leading 0's moved to end).)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2024-04-02.
- ^ Weisstein, Eric W. "Heptagon". mathworld.wolfram.com. Retrieved 2020-08-25.
- ^ Weisstein, Eric W. "7". mathworld.wolfram.com. Retrieved 2020-08-07.
- ^ Weisstein, Eric W. "Dice". mathworld.wolfram.com. Retrieved 2020-08-25.
- ^ Antoni, F. de; Lauro, N.; Rizzi, A. (2012-12-06). COMPSTAT: Proceedings in Computational Statistics, 7th Symposium held in Rome 1986. Springer Science & Business Media. p. 13. ISBN 978-3-642-46890-2.
...every catastrophe can be composed from the set of so called elementary catastrophes, which are of seven fundamental types.
- ^ Massey, William S. (December 1983). "Cross products of vectors in higher dimensional Euclidean spaces" (PDF). The American Mathematical Monthly. 90 (10). Taylor & Francis, Ltd: 697–701. doi:10.2307/2323537. JSTOR 2323537. S2CID 43318100. Zbl 0532.55011. Archived from the original (PDF) on 2021-02-26. Retrieved 2023-02-23.
- ^ Baez, John C. (2002). "The Octonions". Bulletin of the American Mathematical Society. 39 (2). American Mathematical Society: 152–153. doi:10.1090/S0273-0979-01-00934-X. MR 1886087. S2CID 586512.
- ^ Stacey, Blake C. (2021). A First Course in the Sporadic SICs. Cham, Switzerland: Springer. pp. 2–4. ISBN 978-3-030-76104-2. OCLC 1253477267.
- ^ "Millennium Problems | Clay Mathematics Institute". www.claymath.org. Retrieved 2020-08-25.
- ^ "Poincaré Conjecture | Clay Mathematics Institute". 2013-12-15. Archived from the original on 2013-12-15. Retrieved 2020-08-25.
- ^ Georges Ifrah, The Universal History of Numbers: From Prehistory to the Invention of the Computer transl. David Bellos et al. London: The Harvill Press (1998): 395, Fig. 24.67
- ^ Eeva Törmänen (September 8, 2011). "Aamulehti: Opetushallitus harkitsee numero 7 viivan palauttamista". Tekniikka & Talous (in Finnish). Archived from the original on September 17, 2011. Retrieved September 9, 2011.
- ^ "Education writing numerals in grade 1." Archived 2008-10-02 at the Wayback Machine(Russian)
- ^ "Example of teaching materials for pre-schoolers"(French)
- ^ Elli Harju (August 6, 2015). ""Nenosen seiska" teki paluun: Tiesitkö, mistä poikkiviiva on peräisin?". Iltalehti (in Finnish).
- ^ "Μαθηματικά Α' Δημοτικού" [Mathematics for the First Grade] (PDF) (in Greek). Ministry of Education, Research, and Religions. p. 33. Retrieved May 7, 2018.
- ^ Gonzalez, Robbie (4 December 2014). "Why Do People Love The Number Seven?". Gizmodo. Retrieved 20 February 2022.
- ^ Bellos, Alex. "The World's Most Popular Numbers [Excerpt]". Scientific American. Retrieved 20 February 2022.
- ^ Kubovy, Michael; Psotka, Joseph (May 1976). "The predominance of seven and the apparent spontaneity of numerical choices". Journal of Experimental Psychology: Human Perception and Performance. 2 (2): 291–294. doi:10.1037/0096-1523.2.2.291. Retrieved 20 February 2022.
- ^ "Number symbolism – 7".
- ^ "Nāṣir-i Khusraw", An Anthology of Philosophy in Persia, I.B.Tauris, pp. 305–361, 2001, doi:10.5040/9780755610068.ch-008, ISBN 978-1-84511-542-5, retrieved 2020-11-17
- ^ Surah Yusuf 12:46
- ^ Rajarajan, R.K.K. (2020). "Peerless Manifestations of Devī". Carcow Indological Studies (Cracow, Poland). XXII.1: 221–243. doi:10.12797/CIS.22.2020.01.09. S2CID 226326183.
- ^ Rajarajan, R.K.K. (2020). "Sempiternal "Pattiṉi": Archaic Goddess of the vēṅkai-tree to Avant-garde Acaṉāmpikai". Studia Orientalia Electronica (Helsinki, Finland). 8 (1): 120–144. doi:10.23993/store.84803. S2CID 226373749.
- ^ The Origin of the Mystical Number Seven in Mesopotamian Culture: Division by Seven in the Sexagesimal Number System
- ^ "Encyclopædia Britannica "Number Symbolism"". Britannica.com. Retrieved 2012-09-07.
- ^ Klimka, Libertas (2012-03-01). "Senosios baltų mitologijos ir religijos likimas". Lituanistica. 58 (1). doi:10.6001/lituanistica.v58i1.2293. ISSN 0235-716X.
- ^ "Chapter I. The Creative Thesis of Perfection by William S. Sadler, Jr. – Urantia Book – Urantia Foundation". urantia.org. 17 August 2011.
- ^ Yemaya. Santeria Church of the Orishas. Retrieved 25 November 2022
- ^ Ergil, Leyla Yvonne (2021-06-10). "Turkey's talisman superstitions: Evil eyes, pomegranates and more". Daily Sabah. Retrieved 2023-04-05.
References
[edit]- Wells, D. The Penguin Dictionary of Curious and Interesting Numbers London: Penguin Group (1987): 70–71