! symbol

You push shift then 1

n! = n * (n-1) * (n-2)... * 3 * 2 * 1

Example: 5! = 5 * 4 * 3 * 2 * 1 = 120

Also 0! = 1

n! means factorial n.

which is n(n-1)(n-2) ..... 1

e.g.

10! = 10 times 9 times 8 times ...... times 1

      = 3628800