Ruby program to find largest prime factor

primefactor.rb

#Ruby program for find the prime factor of 600851475143
    
    def gen_prime_factors(num) 
      result = []
      2.upto(num-1) do |i| 
       
        result.push i if num % i == 0
        puts "Prime factor found: #{i}" 
      end
      result
    end


puts gen_prime_factors(600851475143).last