# [[2016-10-03] Challenge #286 [Easy] Reverse Factorial](https://www.reddit.com/r/dailyprogrammer/comments/55nior/20161003_challenge_286_easy_reverse_factorial/)

## Description

Nearly everyone is familiar with the factorial operator in math. 5! yields 120
because factorial means "multiply successive terms where each are one less than
the previous":

    5! -> 5 * 4 * 3 * 2 * 1 -> 120

Simple enough. 

Now let's reverse it. Could you write a function that tells us that "120" is
"5!"? 

Hint: The strategy is pretty straightforward, just divide the term by
successively larger terms until you get to "1" as the resultant:

    120 -> 120/2 -> 60/3 -> 20/4 -> 5/5 -> 1 => 5!

## Sample Input

You'll be given a single integer, one per line. Examples:

    120
    150

## Sample Output

Your program should report what each number is as a factorial, or "NONE" if
it's not legitimately a factorial. Examples:

    120 = 5!
    150   NONE

## Challenge Input

    3628800
    479001600
    6
    18

## Challenge Output

    3628800 = 10!
    479001600 = 12!
    6 = 3!
    18  NONE
