Let’s define a function over the non-negative integers in the following manner:
- P(n) = n when n is a one-digit integer.
- P(n) = the product of all the digits of n when n > 9.
Example: P(1729) = 126, because 1 × 7 × 2 × 9 = 126.
Evaluate the following:
Note: this problem was shared to WTM by Reza Kassai, of Shiraz, Iran.