In mathematics, the factorial of a non-negative integer n, denoted by n!, is the product of all positive integers less than or equal to n: n!=nx(n-1)x(n-2)x(n-3).............3x2x1 5! = 5x4x3x2x1 = 120 The value of 0! is 1, according to the convention for an empty product. Factorial of a whole number 'n' is defined as the product of that number with every whole number till 1. For example, the factorial of 4 is 4×3×2×1, which is equal to 24. It is represented using the symbol '!' So, 24 is the value of 4! In the year 1677, Fabian Stedman, a British author, defined factorial as an equivalent of change ringing. Change ringing was a part of the musical performance where the musicians would ring multiple tuned bells. And it was in the year 1808, when a mathematician from France, Christian Kramp, came up with the symbol for factorial: n! The study of factorials is at the root of several topics in mathematics, such as the number theory, algebra, geometry, probability, statistics, graph theory, and discrete mathematics, etc.