I am good at remembering numbers & phone numbers too!. And its similar to what you mentioned. I can recite my whole phonebook if needed, even for numbers punched 15+ years ago.

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)

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?

Yes. We might have been siblings in another life :)

Do you have perfect pitch? What frequencies do the numbers have? How high is the frequency of a really large number like 1000? What about fractions and irrational numbers?

I don't, though I did play piano for 10 years starting at age 6. I think the frequencies are around middle C or so, though I haven't really checked.

Only digits have notes associated with them. A number like 1000 is just four notes in a row. Irrational numbers again are just composed of their digits.

Uh... That's rad! And now I feel even dumber.