Enter a non-negative integer to calculate the factorial result. The factorial of a positive integer is calculated as the product of all positive integers less than or equal to the number.
Tips: Factorial is the arithmetic symbol invented by Kirsten Kaman in 1808 and is a common mathematical term. The factorial of a positive integer is calculated as the product of all positive integers less than or equal to the number, and the factorial of 0 is 1. The factorial of the natural number n is written as n!.