Is the Input Factorial of an Integer?

Create a function that checks if a given integer is exactly the factorial of an integer or not. True if it is, False otherwise.

Examples

is_factorial(2) ➞ True
# 2 = 2 * 1 = 2!

is_factorial(27) ➞ False

is_factorial(24) ➞ True
# 24 = 4 * 3 * 2 * 1 = 4!

Notes

• No error handling is necessary. Inputs are all positive integers.
• Alternatively, you can solve this with a recursive approach.
• There are similar versions of this challenge that is a bit more challenging than this one (a recursive and a non-recursive).