Calculates the digit sum of an integer number

digit_sum.rb

class Integer
  def digit_sum(base = 10)
    result = 0
    number = self
    while(number > 0) do
      result += number % base
      number /= base
    end
    result
  end
end

(2**906).digit_sum     #1234
1234.digit_sum         #10