Graduate Management Admission Test (GMAT) Practice Test

What is the result of 1 factorial (1!)?

1. 0

2. 1

3. 2

4. 3

The correct answer is: 1

The result of 1 factorial, denoted as 1!, is defined as the product of all positive integers up to 1. Since there is only one positive integer in this case, the calculation simplifies to just the integer itself. Therefore, 1! = 1. Factorials are defined for non-negative integers, and by convention, the factorial of 0 (0!) is also defined to be 1. This creates a consistent framework in which the factorial of any positive integer n is n multiplied by the factorial of (n-1), leading back to the base case of 1! = 1. Understanding this foundational concept helps in recognizing that factorials grow quickly as n increases, but for n equal to 1, the output is simply the identity of multiplication for the first integer, which is 1.