Factorial Calculator (n!)

Enter a non-negative integer n to compute the factorial n! exactly, along with its digit count, Stirling approximation, and the previous factorial. Large values are shown in scientific notation.

Input

Enter a non-negative integer n to compute its factorial n!=1×2×…×n.

n (non-negative integer)

Example: enter 10 to compute 10!. Note that 0! equals 1.

Result

Value of 10!

3,628,800

Number of digits

Stirling approximation

3.59869562 × 10 to the power 6

Value of (10−1)!

362,880

The Stirling approximation n!≈√(2πn)×(n/e)^n becomes relatively more accurate as n grows.

How it works

The factorial is defined as n!=1×2×3×…×n, with 0!=1.
The exact value is computed with big integers, so there is no rounding overflow.
The digit count uses the sum of common logarithms log10(1)+log10(2)+…+log10(n).
Stirling approximation n!≈√(2πn)×(n/e)^n is shown as a reference for large n.
When the result has many digits, it is displayed as a mantissa times ten to a power in scientific notation.

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