# factorial

Factorial

The product of a given integer and all smaller positive integers. The factorial of n is written n! and is read aloud "n factorial".

Note: By definition, 0! = 1.

 Formula: n! = n·(n – 1)·(n – 2) · · · 3·2·1 Example: 6! = 6·5·4·3·2·1 = 720