My solution to https://github.com/oozou/challenges/pull/1

raindrops.rb

require 'prime'

class Raindrops
  def self.convert(number)
    factors = number.prime_division.to_h.keys & [3, 5, 7]
    return number.to_s if factors.empty?
    factors.join.tr('357', 'iao').gsub(/(\w)/, 'Pl\1ng')
  end
end