Factorial Calculator (n)

Calculate the factorial of a number, n!.

What is a factorial?

In mathematics, there are n! ways to arrange n objects in sequence. "The factorial n! gives the number of ways in which n objects can be permuted."[1] For example:

• 2 factorial is 2! = 2 x 1 = 2
  -- There are 2 different ways to arrange the numbers 1 through 2. {1,2,} and {2,1}.
• 4 factorial is 4! = 4 x 3 x 2 x 1 = 24
  -- There are 24 different ways to arrange the numbers 1 through 4. {1,2,3,4}, {2,1,3,4}, {2,3,1,4}, {2,3,4,1}, {1,3,2,4} ..... etc.
• 5 factorial is 5! = 5 x 4 x 3 x 2 x 1 = 120
• 0 factorial is a definition: 0! = 1.  There is exactly 1 way to arrange 0 objects.

References

[1] For more information on factorials please see http://mathworld.wolfram.com/Factorial.html