# 5 (number)

(Redirected from ۵)
 ← 4 5 6 →
Cardinal five
Ordinal 5th
(fifth)
Numeral system quinary
Factorization prime
Divisors 1, 5
Roman numeral V
Roman numeral (unicode) Ⅴ, ⅴ
Greek prefix penta-/pent-
Latin prefix quinque-/quinqu-/quint-
Binary 1012
Ternary 123
Quaternary 114
Quinary 105
Senary 56
Octal 58
Duodecimal 512
Vigesimal 520
Base 36 536
Greek ε (or Ε)
Arabic ٥,5
Persian ۵
Urdu
Ge'ez
Bengali
Punjabi
Chinese numeral 五，伍
Korean 다섯,오
Devanāgarī (panch)
Hebrew ה (Hey)
Khmer
Telugu
Malayalam
Tamil

5 (five ) is a number, numeral, and glyph. It is the natural number following 4 and preceding 6.

## In mathematics

Five is the third prime number. Because it can be written as 221+1, five is classified as a Fermat prime; therefore a regular polygon with 5 sides (a regular pentagon) is constructible with compass and unmarked straightedge. 5 is the third Sophie Germain prime, the first safe prime, the third Catalan number, and the third Mersenne prime exponent. Five is the first Wilson prime and the third factorial prime, also an alternating factorial. Five is the first good prime. It is an Eisenstein prime with no imaginary part and real part of the form $3n - 1$. It is also the only number that is part of more than one pair of twin primes. Five is a congruent number. Five is conjectured to be the only odd untouchable number and if this is the case then five will be the only odd prime number that is not the base of an aliquot tree.

The number 5 is the fifth Fibonacci number, being 2 plus 3. 5 is also a Pell number and a Markov number, appearing in solutions to the Markov Diophantine equation: (1, 2, 5), (1, 5, 13), (2, 5, 29), (5, 13, 194), (5, 29, 433), ... ( lists Markov numbers that appear in solutions where one of the other two terms is 5). Whereas 5 is unique in the Fibonacci sequence, in the Perrin sequence 5 is both the fifth and sixth Perrin numbers.

In bases 10 and 20, 5 is a 1-automorphic number.

5 and 6 form a Ruth–Aaron pair under either definition.

There are five solutions to Znám's problem of length 6.

Five is the second Sierpinski number of the first kind, and can be written as S2=(22)+1

While polynomial equations of degree 4 and below can be solved with radicals, equations of degree 5 and higher cannot generally be so solved. This is the Abel–Ruffini theorem. This is related to the fact that the symmetric group Sn is a solvable group for n ≤ 4 and not solvable for n ≥ 5.

While all graphs with 4 or fewer vertices are planar, there exists a graph with 5 vertices which is not planar: K5, the complete graph with 5 vertices.

Five is also the number of Platonic solids.[1]

A polygon with five sides is a pentagon. Figurate numbers representing pentagons (including five) are called pentagonal numbers. Five is also a square pyramidal number.

Five is the only prime number to end in the digit 5, because all other numbers written with a 5 in the ones-place under the decimal system are multiples of five. As a consequence of this, 5 is in base 10 a 1-automorphic number.

Vulgar fractions with 5 or 2 in the denominator do not yield infinite decimal expansions, unlike expansions with all other prime denominators, because they are prime factors of ten, the base. When written in the decimal system, all multiples of 5 will end in either 5 or 0.

There are five Exceptional Lie groups.

## Evolution of the glyph

The evolution of the modern Western glyph for five cannot be neatly traced back to the Indian system as for the numbers 1 to 4. The Kushana and Gupta empires in what is now India had among themselves several different glyphs which bear no resemblance to the modern glyph. The Nagari and Punjabi took these glyphs and all came up with glyphs that are similar to a lowercase "h" rotated 180°. The Ghubar Arabs transformed the glyph in several different ways, producing glyphs that were more similar to the numbers 4 or 3 than to the number 5.[2]

It was from those characters that Europeans finally came up with the modern 5, though from purely graphical evidence, it would be much easier to conclude that the modern symbol came from the Khmer. The Khmer glyph develops from the Kushana/Ândhra/Gupta numeral, its shape looking like the modern version with an extended swirled 'tail' [3]

While the shape of the 5 character has an ascender in most modern typefaces, in typefaces with text figures the character usually has a descender, as, for example, in .

## Religion and culture

Jewish
• The Torah contains five books—Genesis, Exodus, Leviticus, Numbers, and Deuteronomy—which are collectively called the Five Books of Moses, the Pentateuch (Greek for "five containers," referring to the scroll cases in which the books were kept), or Humash (חומש, Hebrew for "fifth").
• The book of Psalms is arranged into five books, paralleling the Five Books of Moses.
• The Khamsa, an ancient symbol shaped like a hand with five fingers, is used as a protective amulet by Jews; that same symbol is also very popular in Arabic culture, known to protect from envy and the evil eye.
Christian
Islamic
Sikh
• The five sacred Sikh symbols prescribed by Guru Gobind Singh are commonly known as Panj Kakars or the 'Five Ks' because they start with letter K representing Kakka (ਕ) in the Punjabi language/Gurmukhi Script. They are: Kesh (unshorn hair), Kangha (the comb), Kara (the steel bracelet), Kachhehra (the soldiers shorts), and Kirpan (the sword) [in Gurmukhi Script: ਕੇਸ, ਕੰਘਾ, ਕੜਾ, ਕਛਹਰਾ, ਕਿਰਪਾਨ]. Also, there are five deadly evils: Kam (lust), Krodh (anger), Moh (attachment), Lobh (greed), and Ankhar (ego).
Discordianism
• In Discordianism, 5 is seen as a very important number. This is demonstrated in the Law of Fives, as well as in the Pentabarf, which contains five rules.
• Each page of the Principia Discordia —the primary religious document in Discordianism— is labeled with five digits.
Other

## Sports

• The Olympic Games have five interlocked rings as their symbol, representing the number of inhabited continents represented by the Olympians (counting North America and South America as one continent).
• Five-a-side football is a variation of association football in which each team fields five players.
• The jersey number 5 has been retired by several North American sports teams in honor of past playing greats or other key figures:
• In baseball scorekeeping, the number 5 represents the third baseman's position.
• The number 5 is used to represent the position of center.
• The number of players of a basketball team on the court at a given time. Thus, the phrase five on five is commonly used to describe standard competitive basketball.
• The "5-second rule" refers to several related rules designed to promote continuous play. In all cases, violation of the rule results in a turnover.
• In all major rulesets, a team has 5 seconds to release the ball toward the court on a throw-in.
• In all major rulesets except that of the NBA, a "closely guarded" player has 5 seconds to shoot, pass, or penetrate past the defender.
• In the NBA only, a player cannot dribble with his back or side to the basket for more than 5 seconds.
• Under FIBA rules, a player has 5 seconds to attempt a free throw. (North American rulesets allow 10 seconds.)
• In Formula One racing, the number 5 & 6 cars traditionally belonged to the Williams team, until the end of the 1995 Formula One season. It was most synonymous with Nigel Mansell in the late 1980s and early 1990s.
• In hockey, the area between the goaltender's legs is known as the five-hole.
• In the NASCAR Sprint Cup Series, the #5 car has been owned by Hendrick Motorsports since 1984. Drivers who have raced in this car during this period include:
• In professional wrestling, if a wrestler grabs the ropes when he is in a submission hold, the attacking wrestler has up to a 5 count to break the hold until a disqualification is made. This is also the case for choking.
• In rugby league:
• In most competitions, the starting left wing wears this number. An exception is the European Super League, which uses static squad numbering.
• The number of tackles the attacking team has to score a try before the handover.
• In rugby union:
• The number of points awarded for a try.
• The number of the starting lock forward who usually jumps at number 4 in the line-out in rugby union.
• The playing field contains two lines that are each 5 metres from the try line. These are significant because no scrum can be set between this line and the try line.
• In cross country the fifth runner is often considered the most important runner to his/her team. In most cases, the points system works where your placement in the overall race scores the amount of points as the number place they came in. For example, the winner of the race will receive one point for their team, the runner-up will receive two for their team, and so on for five runners on any given team. The team with the least amount of points, akin to golf, wins the meet. With that said, the fifth runner can displace runners on another team, pushing them down the rankings, significantly improving a teams chances of winning. On the contrary, some professional athletes, one being Mary Cain, have disagreed. At an interview during the Nike Cross Regionals North East/New York festivities, she claimed that all the runners on a cross country team were important, however the third runner is most important in her point of view. Regardless, one individual, Leonardo Lafond of Andover High School stands firmly in his belief that the fifth runner is clearly the most important runner. During a practice in the midst of the 2013 Merrimack Valley Conference cross country season, Lafond stated while pointing to several runners, "You can beat the number five, you can beat the number five, even you can beat the number five!" This famous line has become an inspirational quote for many runners who are the sixth, seventh, eighth, and even ninth runners on a cross country team.

## Technology

• 5 is the most common number of gears for automobiles with manual transmission.
• In radio communication, the term "Five by five" is used to indicate perfect signal strength and clarity.
• On almost all devices with a numeric keypad such as telephones, computers, etc., the 5 key has a raised dot or raised bar to make dialing easier. Persons who are blind or have low vision find it useful to be able to feel the keys of a telephone. All other numbers can be found with their relative position around the 5 button (on computer keyboards, the 5 key of the numpad has the raised dot or bar, but the 5 key that shifts with % does not).
• On most telephones, the 5 key is associated with the letters J, K, and L, but on some of the BlackBerry phones, it is the key for G and H.
• The Pentium, coined by Intel Corporation, is a fifth-generation x86 architecture microprocessor.
• The resin identification code used in recycling to identify polypropylene.
• A pentamer is an oligomer composed of five sub-units.

## Miscellaneous fields

Five can refer to:

The fives of all four suits in playing cards