What is the Factorial Calculator?
The factorial n! is the product 1 × 2 × 3 × … × n. It counts how many ways n different things can be arranged and grows extremely fast — 20! already has 19 digits.
How to use it
- 1
Enter n
A whole number up to 5000.
- 2
Read or copy the result
With its size.
Features
Exact
Every digit, no rounding, up to 5000!
Digits and zeros
How long it is and how many zeros it ends with.
Copy
The full number in one tap.
Popular uses
Combinatorics
Arrangements and probabilities.
Programming practice
Check big-number results.
Frequently asked questions
What is 0!?
1, by definition.
Why so many trailing zeros?
Each pair of factors 2 and 5 makes a 10.