Composite number

[1][2] Every positive integer is composite, prime, or the unit 1, so the composite numbers are exactly the numbers that are not prime and not a unit.

[2] For example, the composite number 299 can be written as 13 × 23, and the composite number 360 can be written as 23 × 32 × 5; furthermore, this representation is unique up to the order of the factors.

This fact is called the fundamental theorem of arithmetic.

For the latter (where μ is the Möbius function and x is half the total of prime factors), while for the former However, for prime numbers, the function also returns −1 and

If none of its prime factors are repeated, it is called squarefree.

For example, 72 = 23 × 32, all the prime factors are repeated, so 72 is a powerful number.