When you play it many times, your fingers will just run before you even try to remember the notes you were trying to memorize a week ago. This is because you're using your "muscle memory", a lot of hard work to get all the finger positions.
I memorize in another way. To sit down and practice the piece without a piano, imagine the keys of the piano. After just once, you'll get all the notes, bar numbers, expressions etc in memory! =^_____^=