input: Write a python function to check if a number is an Armstrong number.
  assert isArmstrongNumber(1634) == True
  assert isArmstrongNumber(9474) == True
  assert isArmstrongNumber(123) == False
output: def isArmstrongNumber(n):
      digits = list(map(int, str(n)))
      power = len(digits)
      return sum(d ** power for d in digits) == n