Factorial Calculator
Enter a non-negative integer to calculate its factorial (n!), double factorial (n!!), and subfactorial (derangement number !n). Factorials are essential in permutations, combinations, and probability.
Inputs
Max 170 due to floating-point limits
Results
n!
720
6 x 5 x 4 x 3 x 2 x 1 = 720
n!!
48
6 x 4 x 2 = 48
!n (Subfactorial)
265
Number of derangements
Digits in n!
3