input: Write a python function to check if a number is an Armstrong number.
  assert isArmstrong(153) == True
  assert isArmstrong(9474) == True
  assert isArmstrong(9475) == False
output: def isArmstrong(number):
      digits = [int(d) for d in str(number)]
      power = len(digits)
      return number == sum(d ** power for d in digits)