input: Write a python function to check if a number is an Armstrong number.
  assert isArmstrongNumber(153) == True
  assert isArmstrongNumber(9474) == True
  assert isArmstrongNumber(123) == False
output: def isArmstrongNumber(n):
      digits = str(n)
      num_digits = len(digits)
      sum_of_powers = sum(int(digit) ** num_digits for digit in digits)
      return sum_of_powers == n