...OH!
So the factorials are the numeric bases! So instead of for, for example, binary where the digits are 8|4|2|1, so decimal 10 is 1010, in this case the digits are the factorials - 24|6|2|1, right?
So in that case, the maximum value in each digit is the n!, so for the 3rd digit (sixes), the highest that can be is 3, and for the 4th digit (twenty-fours) the highest that can be is 4? And the 5th digit is 120s... let me just... hang on.
4x24 + 3x6 + 2x2 + 1x1 = 119...
Son of a gun it works!!!
In that case...