When I was a teenager, I used to use my mom's credit card to order software for her company. For the last 16 years I have remembered that credit card number. Once, late at night when ordering airline tickets, I accidentally recited that number as my own.
I also installed PageMaker probably 30 times on their computers. The 16-year-old PageMaker serial number is now ingrained in my memory.
On the first day of a class I took as a teenager the professor handed around a signin sheet where we had to write down our name, phone number, and social security number. One of the guys in the class was someone I had met before, so my eye caught his personal data. I have not been able to forget his SSN since.