You will need
In order to calculate the factorial of a number n, you need to use a simple formula: n! = 1 x 2 ... x n. For example, 5! = 1 x 2 x 3 x 4 x 5 = 120. All multiplication operations can be easily done by using the calculator.
If the number, whose factorial we need to calculate is too large, then you will be able to help a table of factorials. Such tables are in the printed version and free online.
Another option to compute the factorial for the lazy, the so – called calculator factorials, outstanding need the answer after carrying out just one operation. This calculator also is in the public domain.