input: from typing import List
  
  
  def is_armstrong_number(num: int) -> bool:
      """ Check if given number is an Armstrong number.
      >>> is_armstrong_number(153)
      True
      >>> is_armstrong_number(123)
      False
      """
output:     digits = [int(d) for d in str(num)]
      num_digits = len(digits)
      armstrong_sum = sum(d ** num_digits for d in digits)
      return armstrong_sum == num