There's a lot of great 4 digit numbers. 1066, 1492, 1665, 1812, 1418, 1939, 4711, 2512, 2001 etc I used to reset the alarm code whenever an employee left and tried to make it easy to remember the new one. Every other or every third digit of a phone number, or an old house number XY(X+!)(Y+1) f'r...