19

This number is a prime.

Just showing those entries submitted by 'Ahmed': (Click here to show all)

19 is the smallest number n such that p = 2n-1 is prime and the digit sums of both p² and p³ equal n. Here p = 37: 37² = 1369 and 37³ = 50653, each with digit sum 19. Notably, the digit sums of 19 and 37 are also equal. [Ahmed]