I can do my bank sort code & account number from memory - but I wouldn't have a chance at my credit card number. I suspect it's something to do with the length of the numbers - the human brain is better at remembering two shorter sequences than one sixteen digit number.

I'm pretty good with memorising numbers in general. One Christmas my family gave me one of those "Improve Your Memory" books containing tricks for memorising long lists of things and (for example) recalling the item at a particular numbered position on demand. The book started off with a quick test - "see how good your memory already is so you know what to try to improve" - and while my short-term recall of word-oriented things was about average, my score on number memory was near-perfect (and my score on matching names to faces was actually perfect, which definitely doesn't seem to reflect my real-life experience).

I've had some trouble with my credit card number since I changed credit cards - I could do the old one with no problem, but I've only just managed to memorise the new one and I still can't remember the expiry date offhand.

But normally, I'd expect to be more familiar with numbers I use a lot, and I think I've used my bank details about three or four times ever.

I happen to have a very memorable account number, and sort codes are only three chunks (I rememebr it as three two-digit numbers, not a six-digit number).