I have very little need to memorize telephone numbers outside of my own or my work line. As such I probably know like 2 - 3 off the cuff if you were to test me. However, if we expand that in to the short codes for my firms offices? Then you'd probably throw that to 30+ easily. I don't need to memorize telephone numbers so I don't. That being said, I have memorized my debit card number in full which is a 16 digit code, plus the expiry and CVC? (another 9 numbers) and the PIN? I could probably memorize a trout ton of numbers if I had to. I just don't feel the need to do it.