Donaldson R F Factorial Calculator
Get the exact value of n! — every digit — for whole numbers up to 10,000.
–Digits
–Trailing zeros
–Scientific notation
What is a factorial?
The factorial of a non-negative whole number n, written n!, is the product of every whole number from 1 to n: 5! = 5 × 4 × 3 × 2 × 1 = 120, and by convention 0! = 1. Factorials grow extremely fast — 20! already has 19 digits and 100! has 158 — so this calculator uses arbitrary-precision integers to show every digit exactly rather than rounding. Factorials count the ways to arrange n distinct items, and appear in permutations, combinations and probability. Trailing zeros come from factors of 10, i.e. pairs of 2 and 5: their number is ⌊n/5⌋ + ⌊n/25⌋ + ⌊n/125⌋ + …