6 (number)

Cardinal	6 six
Ordinal	6th sixth
Numeral system	senary
Factorization
Divisors	1, 2, 3, 6
Roman numeral	VI
Unicode representation of Roman numeral	Ⅵ, ⅵ
prefixes	hexa-/hex- (from Greek) sexa-/sex- (from Latin)
Binary	110
Octal	6
Duodecimal	6
Hexadecimal	6
Hebrew	ו (Vav)

6 (six) is the natural number following 5 and preceding 7.

The SI prefix for 1000⁶ is exa (E), and for its reciprocal atto (a).

Evolution of the glyph

The evolution of our modern glyph for 6 appears rather simple when compared with that for the other numerals. Our modern 6 can be traced back to the Brahmin Indians, who wrote it in one stroke like a cursive lowercase e rotated 45 degrees clockwise. Gradually, the upper part of the stroke (above the central squiggle) became more curved, while the lower part of the stroke (below the central squiggle) became straighter. The Ghubar Arabs dropped the part of the stroke below the squiggle. From there, the European evolution to our modern 6 was very straightforward, aside from a flirtation with a glyph that looked more like an uppercase G.

On the seven-segment displays of calculators and watches, 6 is usually written with six segments. Some historical calculator models use just five segments for the 6, by omitting the top horizontal bar. This glyph variant has not caught on. For calculators that can display results in hexadecimal, a 6 that looks like a B is not practical.

In mathematics

Six is the second smallest composite number, its proper divisors being 1, 2 and 3. Since six equals the sum of these proper divisors, six is a perfect number. As a perfect number, 6 is related to the Mersenne prime 3, since 2¹(2² - 1) = 6. The next perfect number is 28. Six is also a unitary perfect number, a harmonic divisor number and a highly composite number. The next highly composite number is 12.

The smallest non-abelian group is the symmetric group S₃ which has 3! = 6 elements. S₆ itself, with 720 elements, is the only finite symmetric group which has an outer automorphism.

In binary code, six is 110; in ternary code six is 20; in quaternary numeral system code six is 12; in quinary six is 11; in senary six is 10; in septenary code and all codes above (such as octal, decimal and hexadecimal) six is 6. Since it is divisible by the sum of its digits in all these bases, 6 is one of the four all-Harshad numbers.

A six-sided polygon is a hexagon. Figurate numbers representing hexagons (including six) are called hexagonal numbers. Six is also an octahedral number. It is a triangular number and so is its square (36).

In base 10, 6 is a 1-automorphic number.

In science

• The atomic number of carbon.
• The number of carbon atoms and carbon-carbon bonds in benzene.

In astronomy,

Messier object M6, a magnitude 4.5 open cluster in the constellation Scorpius, also known as the Butterfly Cluster.

The New General Catalogue object NGC 6 , a spiral galaxy in the constellation Andromeda

The Saros number of the solar eclipse series which began on -2691 March 16 and ended on -1393 May 3. The duration of Saros series 6 was 1298.1 years, and it contained 73 solar eclipses.

The Saros number of the lunar eclipse series which began on -2642 July 25 and ended on -1091 February 10. The duration of Saros series 6 was 1550.6 years, and it contained 87 lunar eclipses.

In other fields

Six is:

• In the ancient Roman calendar, Sextilis was the sixth month. After the Julian reform, June is the sixth month and Sextilis was renamed August.
• Where Friday or Saturday is the sixth day of the week varies across cultures.
• Sextidi was the sixth day of the decade in the French Revolutionary calendar.
• In cricket, a "six" or "sixer" is a shot in which the ball clears the boundary without bouncing, scoring six runs. See cricket terminology.
• In American Football, the number of points received for a touchdown.
• In rugby union, the position of blindside flanker.
• In baseball, six represents the shortstop's position.
• The length in years of a standard term of a United States senator.
• The name of the smallest group of Cub Scouts, traditionally consisting of six people and is led by a 'sixer'. Logically speaking, this isn't always the case, particularly in packs with less than 6 Cub Scouts in it.
• The number of cans in a six-pack .
• The number of feet below ground level a coffin is traditionally buried; thus, the phrase "six feet under" means that a person (or thing, or concept) is dead.
• The number of inhabited continents, and the total number of continents if Eurasia (Europe plus Asia) is considered a single continent.
• The number of large geyser fields in the world.
• The number of points on a Star of David.
• In Astrology, Virgo is the 6th astrological sign of the Zodiac.
• The number of similar coins that can be arranged around a central seventh coin of the same kind so that each coin makes contact with the central one and touches both its neighbors without a gap; see also Sphere packing.
• The number of strings on a standard guitar.
• The number of basic holes or keys on most woodwind instruments (e.g., pennywhistle, clarinet, saxophone, bassoon). These holes or keys are usually not given numbers or letters in the fingering charts.
• The first number where counting on your fingers requires two hands.
• The number of sides on a cube, hence the highest number on a standard die.
• The highest number on one end of a standard domino.

In addition:

• Number Six was the main character in the television series The Prisoner.
• Number Six is a character in the television mini-series and series Battlestar Galactica (2003).
• "Six Geese a Laying" were given as a present on the sixth day in the popular Christmas carol The Twelve Days of Christmas.
• Les Six were a group of Lost Generation writers.
• One of A. A. Milne's poetry books was entitled Now We Are Six.
• Extra-sensory perception is sometimes called the "sixth sense".
• Bands with the number six in their name include Eve 6, Sixpence None the Richer and Los Xey (sei is Basque for "six").
• The Six dynasties form part of Chinese history.
• The Bionic Six are the heroes of an animated series.
• The Birmingham Six were held in prison for 16 years.
• Six Degrees of Kevin Bacon is a game that can be played with the names of actors and actresses.
• RIASEC is a system that places occupations into six categories.
• 666 is considered the Number of the Beast.
• The year "6" can refer to: A.D. 6, 6 B.C., or 1906.

Hexa is Greek for "six". Thus:

• A hexahedron is a polyhedron with six faces, with a cube being a special case.
• An hexagon is a regular polygon with six sides.
  • L' Hexagone is a French nickname for the continental part of France.
• A hexapod is an animal with six legs; this includes all insects.
• Hexameter is a poetic form consisting of six feet per line.
• "Hexadecimal" combines hexa- with the Latinate decimal to name a number base of 16.

The prefix "hexa-" also occurs in the systematic name of many chemical compounds, such as "hexamethyl ".

Sex- is a Latin prefix meaning "six". Thus:

• A group of six musicians is called a sextet.
• Six babies delivered in one birth are sextuplets. The first set of sextuplets of whom all six survived are the Dilley Sextuplets .
• People with sexdactyly have six fingers on each hand.
• The measuring instrument called a sextant got its name because its shape forms one sixth of a whole circle.

If you lift your right foot off the ground, begin moving it in a clockwise circle, and then use your right hand to draw a number 6 in the air, your foot will change directions.