Flip a number without changing it to string

funcs.rb

def flipnum num
  res = 0
  mag = magnitude(num)
  neg = true if num < 0
  num = num.abs
  while num > 0
    mag -= 1
    res += (num % 10)* 10 ** mag
    num = num/10
  end
  unless neg
    res
  else
    res * -1
  end
end

def magnitude num
  num = num.abs
  count = 0
  while num > 0
    count += 1
    num = num/10
  end
  count
end