Enter a whole number from 0 to 20 and the calculator returns its factorial along with the full multiplication expansion.
n! is the product of all positive integers up to n, so 5! = 5 × 4 × 3 × 2 × 1 = 120.
0! is defined as 1, a convention that keeps combinatorics formulas consistent.
20! is the largest factorial that fits exactly in a standard 64-bit number without losing precision.