The factors of 27 are 1,3,9 and 27. That’s four factors. That's why door 27 is closed at the end of the open/closing process - employees 1,3,9 and 27 touch the door and so the final state of the door is the same as the initial state of the door.

Maybe you are talking about the number of prime factors. This quantity is irrelevant to door open/closing problem.