Do you really think it’s a coincidence that the Dewey number for sex is 613.95?
I don’t have a library card (though I’m not sure whether I should feel guilty about that or not). 
I haven’t used it in a while, but I do remember it. That comes from having to log in to check by account status online.
I also know my car’s VIN. A girl at the parts counter thought it was unusual when she asked for it out of the blue and I just rattled it off. When I bought it I had to fill out so many forms, run Carfax reports and all.
I knew my work (academic library) and my local public library one before I moved this summer.
Here, I don’t know them at all. I’m at the point where I almost know the public library one, but just enough to screw it up each time I punch it in.
I’m a librarian, and I do not remember my card number. That’s because, like many librarians, I don’t remember a time when I didn’t have too much in fines to check anything out.
I have mine memorized, but it’s all of 6 digits long with only 3 unique digits. I use the card a lot, too. I’d worry if I *couldn’t *remember it.
Back when I worked for a systems vendor Erie was one of my customers. I remember the stupidest stuff about my time in that job. The barcode prefixes of several of my customers are some of the more useless bits.
Of course, if I just used it to amuse a doper, is it really useless information?