Factorial code

A factorial code is a way to make very large numbers easier to work with. For example, 3 x 4 x 5 is the same as saying 3 factorial (written as 3!).
Factorials are written out by multiplying a number by every number that comes before it starting with 1. So 3 factorial is written as 3! and it is equal to 3 x 2 x 1, which is equal to 6. To find 4! we need to multiply 4 x 3 x 2 x 1, which is equal to 24. And 5! is equal to 5 x 4 x 3 x 2 x 1, which is equal to 120.