5

5 (five) is a positive integer following 4 and preceding 6. Its ordinal form is written "fifth" or "5th".
== Properties ==
*5 is an . Since 10 is a multiple of 5, divisibility by 5 can be easily tested in the decimal system — multiples of 5 always end in 0 or 5. 5 is a : + 1 = 5.
*A 5-sided star is known as a pentagram.
*It is thought that 5 is the only odd .MathWorld, Untouchable Number
*The base five numeral system is called or pental.
== In googology ==
*Some googologisms based on 5 are superpent, googolquinplex and quintoogol. 5 is the length of the Goodstein sequence starting with 3, which goes 3, 3, 3, 2, 1.
*In Greek-based number naming systems, 5 is associated with prefix penta-, and with prefix quinti- in Latin systems.
*Flan number 5 version 2 (or フラン数第五形態改二 in Japanese) is equal to 5.
=== Googological functions returning 5 ===
*Goodstein function: \(G(3)=5\)
*Weak Goodstein function: \(g(3)=5\)
*Laver table: \(q(3)=5\)
*Weak tree function: \(\text{tree}(2)=5\)
*Friedman's circle theorem: \(\text{Circle}(1)=5\)
*simple subcubic graph number: \(\text{SSCG}(1)=5\)
== As a cash denomination ==
Some currencies, such as the and the , have banknotes with this number in the denomination.
Some currencies, such as the , the (shekel-wise and formerly Agorot-wise) and the , have coins with this number in the denomination.
== Sources ==
cs:5
es:5
Category:Numbers
Category:Banknote denominations
Category:Class 0
Category:Coin denominations
Category:Fibonacci numbers
Category:Numbers 0-99
Category:Palindromic prime numbers
 
Category:Prime numbers