12 (number)

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111213
Cardinaltwelve
Ordinal12th
(twelfth)
Factorization22× 3
Divisors1, 2, 3, 4, 6, 12
Roman numeralXII
Greek prefixdodeca-
Latin prefixduodeca-
Binary11002
Ternary1103
Quaternary304
Quinary225
Senary206
Octal148
Duodecimal1012
HexadecimalC16
VigesimalC20
Base 36C36
 
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111213
Cardinaltwelve
Ordinal12th
(twelfth)
Factorization22× 3
Divisors1, 2, 3, 4, 6, 12
Roman numeralXII
Greek prefixdodeca-
Latin prefixduodeca-
Binary11002
Ternary1103
Quaternary304
Quinary225
Senary206
Octal148
Duodecimal1012
HexadecimalC16
VigesimalC20
Base 36C36
Mathematical properties
φ(12) = 4τ(12) = 6
σ(12) = 28π(12) = 5
μ(12) = 0M(12) = -2

12 (twelve Listeni/ˈtwɛlv/) is the natural number following 11 and preceding 13.

The word "twelve" is the largest number with a single-morpheme name in English. Etymology suggests that "twelve" (similar to "eleven") arises from the Germanic compound twalif "two-leftover", so a literal translation would yield "two remaining [after having ten taken]".[1] This compound meaning may have been transparent to speakers of Old English, but the modern form "twelve" is quite opaque. Only the remaining tw- hints that twelve and two are related.

A group of twelve things is called a duodecad. The ordinal adjective is duodecimal, twelfth. The adjective referring to a group consisting of twelve things is duodecuple.

The number twelve is often used as a sales unit in trade, and is often referred to as a dozen. Twelve dozen are known as a gross. (Note that there are thirteen items in a baker's dozen.)

As shown below, the number twelve is frequently cited in the Abrahamic religions and is also central to the Western calendar and units of time.

In mathematics[edit]

Twelve is a composite number, the smallest number with exactly six divisors, its divisors being 1, 2, 3, 4, 6 and 12. Twelve is also a highly composite number, the next one being twenty four. Twelve is also a superior highly composite number, the next one being sixty. It is the first composite number of the form p2q; a square-prime, and also the first member of the (p2) family in this form. 12 has an aliquot sum of 16 (133% in abundance). Accordingly, 12 is the first abundant number (in fact a superabundant number) and demonstrates an 8 member aliquot sequence; {12,16,15,9,4,3,1,0} 12 is the 3rd composite number in the 3-aliquot tree. The only number which has 12 as its aliquot sum is the square 121. Only 2 other square primes are abundant (18 and 20).

Twelve is a sublime number, a number that has a perfect number of divisors, and the sum of its divisors is also a perfect number. Since there is a subset of 12's proper divisors that add up to 12 (all of them but with 4 excluded), 12 is a semiperfect number.

If an odd perfect number is of the form 12k + 1, it has at least twelve distinct prime factors.

Twelve is a superfactorial, being the product of the first three factorials. Twelve being the product of three and four, the first four positive integers show up in the equation 12 = 3 × 4, which can be continued with the equation 56 = 7 × 8.

Twelve is the ninth Perrin number, preceded in the sequence by 5, 7, 10, and also appears in the Padovan sequence, preceded by the terms 5, 7, 9 (it is the sum of the first two of these). It is the fourth Pell number, preceded in the sequence by 2 and 5 (it is the sum of the former plus twice the latter).

A twelve-sided polygon is a dodecagon. A twelve-faced polyhedron is a dodecahedron. Regular cubes and octahedrons both have 12 edges, while regular icosahedrons have 12 vertices. Twelve is a pentagonal number. The densest three-dimensional lattice sphere packing has each sphere touching 12 others, and this is almost certainly true for any arrangement of spheres (the Kepler conjecture). Twelve is also the kissing number in three dimensions.

Twelve is the smallest weight for which a cusp form exists. This cusp form is the discriminant Δ(q) whose Fourier coefficients are given by the Ramanujan τ-function and which is (up to a constant multiplier) the 24th power of the Dedekind eta function. This fact is related to a constellation of interesting appearances of the number twelve in mathematics ranging from the value of the Riemann zeta function function at −1 i.e. ζ(−1) = −1/12, the fact that the abelianization of SL(2,Z) has twelve elements, and even the properties of lattice polygons.

There are twelve Jacobian elliptic functions and twelve cubic distance-transitive graphs.

There are 12 Latin squares of size 3×3.

The duodecimal system (1210 [twelve] = 1012), which is the use of 12 as a division factor for many ancient and medieval weights and measures, including hours, probably originates from Mesopotamia.

In base thirteen and higher bases (such as hexadecimal), twelve is represented as C. In base 10, the number 12 is a Harshad number.

List of basic calculations[edit]

Multiplication12345678910111213141516171819202122232425501001000
12 \times x1224364860728496108120132144156168180192204216228240252264276288300600120012000
Division123456789101112131415
 12 \div x126432.42\mathrm{1.\overline{714285}}1.5\mathrm{1.\overline{3}}1.2\mathrm{1.\overline{09}}1\mathrm{0.\overline{923076}}\mathrm{0.\overline{857142}}0.8
x \div 12\mathrm{0.08\overline{3}}\mathrm{0.1\overline{6}}0.25\mathrm{0.\overline{3}}\mathrm{0.41\overline{6}}0.5\mathrm{0.58\overline{3}}\mathrm{0.\overline{6}}0.75\mathrm{0.8\overline{3}}\mathrm{0.91\overline{6}}1\mathrm{1.08\overline{3}}\mathrm{1.1\overline{6}}1.25
Exponentiation12345678910111213
12 ^ x\,121441728207362488322985984358318084299816965159780352619173642247430083706888916100448256106993205379072
x ^ {12}\,14096531441167772162441406252176782336138412872016871947673628242953648110000000000003138428376721891610044825623298085122481

In numeral systems[edit]

١٢ArabicԺԲArmenian
১২BanglaΔΙΙAttic Greek
יבHebrew
V20Z1Z1
Egyptian
१२Indian & Nepali (Devanāgarī)十二Chinese and Japanese
௧௨TamilRoman and Etruscan
๑๒ThaiIIXChuvash
౧౨Telugu١٢Urdu
ιβʹIonian Greek൧൨Malayalam

In science[edit]

Astronomy[edit]

In religion and mythology[edit]

There are twelve "Jyotirlingas" in Hindu Shaivism. The Shaivites (orthodox devotees of God Shiva) treat them with great respect and they are visited by almost every pious Hindu at least once in a lifetime. The number 12 is very important in many religions, mainly Judaism, Christianity, and Islam, and also found in some older religions and belief systems.

In antiquity there are numerous magical/religious uses of twelves.[2] Ancient Greek religion, the Twelve Olympians were the principal gods of the pantheon and Heracles enacted out twelve labours. The chief Norse god, Odin, had 12 sons. Several sets of twelve cities are identified in history as a dodecapolis, the most familiar being the Etruscan League. In the King Arthur Legend, Arthur is said to have subdued 12 rebel princes and to have won 12 great battles against Saxon invaders. [source: Benet's Reader's Encyclopedia, 3d ed]

The importance of 12 in Judaism and Christianity can be found in the Bible. The biblical Jacob had 12 sons, who were the progenitors of the Twelve Tribes of Israel, while the New Testament describes twelve apostles of Jesus; when Judas Iscariot was disgraced, a meeting was held (Acts) to add Matthias to complete the number twelve once more. (Today, The Church of Jesus Christ of Latter-day Saints has a Quorum of the Twelve Apostles.)

The Book of Revelation contains much numerical symbolism, and a lot of the numbers mentioned have 12 as a divisor. 12:1 mentions a woman—interpreted as the people of Israel, the Church or the Virgin Mary—wearing a crown of twelve stars (representing each of the twelve tribes of Israel). Furthermore, there are 12,000 people sealed from each of the twelve tribes of Israel, making a total of 144,000 (which is the square of 12 multiplied by a thousand).

In Orthodox Judaism, 12 signifies the age a girl matures (bat mitzvah)

There are 12 days of Christmas. The song Twelve Days of Christmas came from the traditional practice of extending Yuletide celebrations over the twelve days from Christmas day to the eve of Epiphany; the period of thirteen days including Epiphany is sometimes known as Christmastide. Thus Twelfth Night is another name for the twelfth day of Christmas or January 5 (the eve of Epiphany). Similarly, Eastern Orthodoxy observes 12 Great Feasts.

In Twelver Shi'a Islam, there are twelve Imams, legitimate successors of the prophet Muhammad. These twelve early leaders of Islam are—Ali, Hasan, Husayn, and nine of Husayn's descendants.

Imāmah (Arabic: إمامة) is the Shī‘ah doctrine of religious, spiritual and political leadership of the Ummah. The Shī‘ah believe that the A'immah ("Imams") are the true Caliphs or rightful successors of Muḥammad, and Twelver and Ismā‘īlī Shī‘ah further that Imams are possessed of supernatural knowledge, authority, and infallibility (‘Iṣmah) as well as being part of the Ahl al-Bayt, the family of Muhammad.[1] Both beliefs distinguish the Shī‘ah from Sunnis.

In Quran, the Sura number 12 is Sura Yusuf (Joseph), and it is located in Juz'a (Arabic : الجزء) number 12. This Sura narrates the story of Prophet Yusuf and his 12 brothers.

In Hinduism, the sun god Surya has 12 names. Also, there are 12 Petals in Anahata (Heart Chakra.)

In time[edit]

In sports[edit]

In the rugby codes:

In both soccer and American football, the number 12 can be a symbolic reference to the fans because of the support they give to the 11 players on the field. Texas A&M University reserves the number 12 jersey for a walk-on player who represents the original "12th Man", a fan who was asked to play when the team's reserves were low in a college American football game in 1922. Similarly, Bayern Munich, Hammarby, Feyenoord, Atlético Mineiro, Flamengo, Seattle Seahawks, Portsmouth and Cork City do not allow field players to wear the number 12 on their jersey because it is reserved for their supporters.

The jersey number 12 has been retired by several North American sports teams in honor of past playing greats (or, in one case, a team's fans):

In Canadian football, 12 is the maximum number of players that can be on the field of play for each team at any time.

In ten-pin bowling, 12 is the number of strikes needed for a perfect game.

In curling, the House or the circular scoring area, is 12 feet in diameter.

In cricket, another sport with eleven players per team, teams may select a "12th man", who may replace an injured player for the purpose of fielding (but not batting, bowling or keeping wicket).

In association football, 12 was also the number of teams in the finals of the FIFA Women's World Cup in its first two editions in 1991 and 1995.

In technology[edit]

In the arts[edit]

Film[edit]

Movies with the number twelve or its variations in their titles include

Television[edit]

Theatre[edit]

Literature[edit]

Music[edit]

Art theory[edit]

Games[edit]

In other fields[edit]

12 stars are featured on the Flag of Europe

See also[edit]

Notes[edit]

  1. ^ http://www.etymonline.com/index.php?term=twelve
  2. ^ The classic assembly of instances is Th. Weinreich, "Zwölfgötten' in W.H. Roscher, Ausfurliches Lexikon der Griechischen und Römishen Mythologie vol. vi. col. 764-848, noted in Robert Drews, "Light from Anatolia on the Roman Fasces"The American Journal of Philology 93.1 (January 1972) pp. 40-51) p 43 note 10. The twelve lictors carried fasces of twelve rods.

References[edit]