"I'm sorry, but you have the wrong number....

...You are looking for Randy. This is Randy's student card."

It took me about 4 years to memorize my student number. Though this past September, after enjoying the privilege of not needing to reach into my pocket for my student card for about a year, I got a phone number that (a) starts out with the same three numbers as my student number and (b) uses only one number that my student number doesn't (though the numbers are not in the same order, disregarding some nonsense about cyclic permutations. I'd say something about Hamming distance, but those who would understand what I mean are probably already thinking it.).

Now, when I give out my phone number, I'm not sure whether I'm giving them my student number or my phone number, and also it takes me quite a while to remember my student number with a significant degree of confidence before I say it out loud.

The mind ends in more ways than one.