How it is calculated
The exact integer is shown up to and including 18. After that, an ordinary browser number no longer keeps every digit.
n! = 1 × 2 × … × n
Where the numbers come from
- Number
Example
5! = 1 × 2 × 3 × 4 × 5 = 120.
Questions
Why does 0! equal 1?
That is the convention, so combination formulas do not break on an empty product.
A fractional factorial?
Integers only. The gamma function for fractions is not calculated.
Why is the ceiling 18?
19! no longer fits in JavaScript's exact integers.