This is an old story about young people that can't remember as much as old people:
This summer, neuroscientist Ian Robertson polled 3,000 people and found that the younger ones were less able than their elders to recall standard personal info. When Robertson asked his subjects to tell them a relativeâs birth date, 87 percent of respondents over age 50 could recite it, while less than 40 percent of those under 30 could do so. And when he asked them their own phone number, fully one-third of the youngsters drew a blank. They had to whip out their handsets to look it up.
For phone numbers there is a simple explanation why we don't remember it. In the past your phone number, was the phone number of your house. If you're not the only person living there, then you have to call it sometimes. You use the number and therefore remember it.
Younger people have mobile phones and these are their main way for communicating with other people. The difference is that you don't have to call this phone ever. Only other people have to call this number. This means the only time when you use this number is when you give it to other people. If you haven't given your number to someone else, then you don't know it.
In my case it's like this: I remember eight character passwords combined from letters and numbers, but I have to type them a few times before I remember, but after that I never forget.
In the same way I remember a few phone numbers of friends that I had to call a few times even after five years.
To remember these numbers, passwords and little bits of information you need to use them a few times, to make it part of your memory, to integrate it.