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Factorial Calculator

Calculate the factorial n! of any whole number up to 5,000 exactly, with the number of digits, trailing zeros and scientific notation. Free.

20!
2,432,902,008,176,640,000
Digits
19
Scientific notation
2.432902 × 10^18
Trailing zeros
4

Factorials grow fast

The factorial n! is the product of every whole number from 1 to n: 5! = 5 × 4 × 3 × 2 × 1 = 120, and 0! is defined as 1. Factorials count the ways to arrange things: 10 books can be ordered in 10! = 3,628,800 ways. They grow faster than exponential growth: 20! = 2,432,902,008,176,640,000, and 100! has 158 digits, ending in 24 zeros. This calculator works with exact whole numbers, so every digit is correct.

How to use it

  1. 1

    Enter n

    A whole number from 0 to 5,000.

  2. 2

    Read n!

    The exact value, digit by digit.

  3. 3

    See the details

    Number of digits, trailing zeros and scientific notation.

Frequently asked questions

Why is 0! equal to 1?

There's exactly one way to arrange nothing, and it keeps formulas like n! = n × (n − 1)! consistent.

How many trailing zeros does n! have?

Count the factors of 5: ⌊n/5⌋ + ⌊n/25⌋ + ⌊n/125⌋ + …. 100! has 20 + 4 = 24.

Can I take the factorial of a decimal?

Not as n!. The gamma function extends factorials to decimals: Γ(n + 1) = n!.

Is anything stored?

No. The calculation runs in your browser.

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