Forgotten Pin Code

You have been using a 4 digit pin code to lock your phone that, no matter how much you are trying now, can’t seem to recall. Tilting your phone at an angle towards the window so that the sunlight shines on it, you see fingerprints. You see that there are 4 fingerprints distinctly appearing on the spots where the numeric buttons appear on the lock screen. You remember that the 4 digits you used were unique (i.e. you didn’t have repeating digits in your pin code), and that the pin code itself was a 4 digit prime number.

This is a companion discussion topic for the original entry at