2! = 2 . 1 = 2
3! = 3 . 2 . 1 = 6
5! = 5 . 4 . 3 . 2 . 1 = 120
11! = 11 . 10 . 9 . 8 . 7 . 6 . 5 . 4 . 3 . 2 . 1 = 39916800
17! = 17 . 16 . 15 . 14 . 13 . 12 . 11 . 10 . 9 . 8 . 7 . 6 . 5 . 4 . 3 . 2 . 1 = 355687428096000
