# Factorial of a Number

**Formula:**`n! = n × (n-1) × (n-2) × ... × 1`

## Understanding Factorial of a Number

The factorial of a non-negative integer ** n**, denoted by

**, is the product of all positive integers less than or equal to**

*n!***. By convention, the value of 0! is 1. It is not defined for negative numbers, and it's usage is widely seen in permutations, combinations, and binomial theorem.**

*n*## Parameter usage:

`n`

= a non-negative integer for which we want to compute the factorial.

## Output:

The function returns the factorial value of the provided integer ** n**.

## Data validation

An error is returned if the input is not a non-negative integer.

## Summary

The calculator computes the factorial value for a given non-negative integer value. It is a fundamental function in combinatorics and helps in calculating combinations and permutations.

Tags: Math, Factorial, Combinatorics