Factorial Calculator

Factorial – Quick Cheat Sheet

• Definition: n! = n × (n−1) × … × 2 × 1, with 0! = 1.
• Growth: Grows super fast. Digits ≈ ⌊log10(n!)⌋ + 1.
• Trailing zeros: ∑⌊n/5⌋ + ⌊n/25⌋ + ⌊n/125⌋ + … (number of factor-of-10s).
• Scientific form: n! ≈ m × 10^e where e = ⌊log10(n!)⌋ and m = 10^{ {log10(n!) − e} }.
• Tips: Use exact output for moderate n; for very large n, rely on digits/trailing-zeros/sci-approx.