Six (6) is a positive integer one more than
5 and one less than 7.
6 is the second
composite number and the first to not be a power. Its factorization is 2* 3. The next composite number is 8 and the previous is 4. It is the second semiprime number, between 4 and 9.
6 is the third
triangular number (between 3 and 10).
6 is the third
factorial number, between 2 and 24. It is also the second primorial number (between 2 and 30). It is the only number after 2 to be both a factorial and primorial.
6 is the first
perfect number, because 1+2+3 = 6. The next perfect number is 28.
6 is the fourth
highly composite number, the first with 4 factors. The next is 12 and the previous is 4.
6 is equal to the sum of its proper divisors:
1 + 2 + 3 = 6. This makes it a perfect number, and in fact the smallest number with that property, with the next being 28.
In Czech language, 6 is called "půltucet", meaning "half-twelve".
Some googologisms based on 6 are
sextoogol, superhex and
File:Six.jpg hexalogue. It is not commonly found in googology.
Six is the base of
Robert Munafo's idea of classes. 6 is the boundary between class 0 and class 1 numbers, 10 is the boundary between class 1 and class 2 numbers, 6 10 is the boundary between class 2 and class 3 numbers, and so on.
In Greek-based number naming systems, 6 is associated with prefix hexa-, and with prefix sex- in Latin systems.
Donald Knuth calls this number sextiad, and it's equal to using the -yllion system.
Jim Blowers calls this number threxclamation.
Robert Muñafo calls this number minimusmillion.