class Faker::Company

def mod11(number)
  weight = [2, 3, 4, 5, 6, 7,
            2, 3, 4, 5, 6, 7,
            2, 3, 4, 5, 6, 7]
  sum = 0
  number.to_s.reverse.chars.each_with_index do |char, i|
    sum += char.to_i * weight[i]
  end
  remainder = sum % 11
  case remainder
  when 0 then remainder
  when 1 then nil
  else 11 - remainder
  end
end