Sadly I no longer know my friends phone numbers, since the advent of smart phones. But I still know the phone numbers of anyone I regularly dialed as a child, 30 years ago.
I have all my important numbers memorized - SIN, multiple credit cards, driver's license, library card, health cards, all my financial account numbers, and the same for my partner. Do you do that too?
I see numbers as notes. So each unique number - say my college ID, my aunt's cell number or my driving license is a MIDI tune in my head.
Also, visually each number is like a 'identity' - not a numeral. When I had a image processing class, running an edge detector on binary images was fun. I could guess the potrait/image just looking at the numbers (just like how you'd guess animal shapes in a connect-the-dots game)