1、One of the counting numbers, used to indicate position.
2、"For any whole number, the product of all the counting numbers up to and including itself. It is indicated with an exclamation point: 4! (read "four factorial") is 1 × 2 × 3 ×4 = 24. "
3、These are not the most important numbers. The real numbers are accrual accounting numbers, and we almost never hear them.
