I have always liked looking at numbers in non-numeric ways, noticing when they are the same right-side up as upside down (1961 carved in a doorstep can be read walking in either direction) or when they work as palindromes.
I am fond of the number 217 and would play it on the lottery if I played the lottery, because it looks like my nickname, upside down.
When I lived in Boston, years ago, the phone number 936 + any four digits got you the weather forecast. This was useful to know when someone was asking you for a number and you didn't want to give them yours, because 936-4527, for example, sounded plausible. Somewhere along the line, my apartment mate and I figured out that you could also remember the weather number as WENDELL, and so checking the weather became "calling Wendell."