Power digit sum
Author: L. Grondin
https://projecteuler.net/problem=16
2^15 = 32768 and the sum of its digits is 3 + 2 + 7 + 6 + 8 = 26.
What is the sum of the digits of the number 2^1000?
Source code: prob016-grondilu.pl
use v6; say 2**1000 .comb.sum;