input: Write a python function to check if a number is an Armstrong number.
  assert armstrong_number(370) == True
  assert armstrong_number(153) == True
  assert armstrong_number(9474) == True
  assert armstrong_number(9475) == False
  assert armstrong_number(10) == False
output: def armstrong_number(num):
      order = len(str(num))
      sum_of_powers = sum(int(digit) ** order for digit in str(num))
      return sum_of_powers == num