Project Euler 12 in ruby

class Integer
  
  # overwritten, I don't need modulus
  def sum_progression
    self * (self + 1) / 2
  end
  
  def integral_divisors_size
    factors = self.factors
    result = 1
    factors.uniq.each do |prime|
      result *= (factors.count(prime) + 1)
    end
    result
  end
  
end