The number itself is also included in the multiplication. So, 10 factorial (also written as 10!) is: 1 x 2 x 3 x 4 x 5 x 6 x 7 x 8 x 9 x 10 = 3,628,800. Five factorial (or 5!) is: 1 x 2 x 3 x 4 x 5 = ...