Problem Statement

Smith numbers are numbers such that the sum of the decimal digits of the integers that make up that number is the same as the sum of the decimal digits of its prime factors excluding 1. By definition, all primes are excluded as they (naturally) satisfy this condition! Smith numbers are also known as   joke   numbers.

Using the number 166 Find the prime factors of 166 which are: 2 x 83 Then, take those two prime factors and sum all their decimal digits: 2 + 8 + 3 which is 13 Then, take the decimal digits of 166 and add their decimal digits: 1 + 6 + 6 which is 13 Therefore, the number 166 is a Smith number.

Write a program to find all Smith numbers below 10000.

Let's start with the solution:

use ntheory qw/:all/;
my @smith;
forcomposites {
  push @smith, $_  if sumdigits($_) == sumdigits(join("",factor($_)));
} 10000-1;
say scalar(@smith), " Smith numbers below 10000.";
say "@smith";


use ntheory ":all";
my $t=0;
forfactored { $t++ if @_ > 1 && sumdigits($_) == sumdigits(join "",@_); } 10**8;
say $t;