# Largest prime factor

*Author: Mark A. Hershberger*

https://projecteuler.net/problem=3

The prime factors of 13195 are 5, 7, 13 and 29.

What is the largest prime factor of the number 600851475143 ?

Source code: prob003-hexmode.pl

use v6; class Prime { has @!primes; has Int $!number = 1; method next() { my $not_prime = 1; while $not_prime && $!number++ { $not_prime = @!primes.grep({$!number % $^a == 0}); } @!primes.push($!number); my $copy = $!number; return $copy; } } my $number = 600851475143; my $prime = Prime.new; my $current-prime; my @primes = gather repeat { $current-prime = $prime.next; if $number %% $current-prime { take $current-prime; $number /= $current-prime; } } while ($current-prime < $number); say @primes.max;