I'm pleased to see that someone has found a prime number with 17,425,170 digits. This is going to come in very handy.
Right after the 1980 census, I was on a radio call-in show where someone asked why, when they filled out their census forms, they had to give their phone number. I explained that the idea was to get the phone number of everyone in the country, add them all together, divide by the total population and then arrive at The Average American Phone Number. A little later, someone called in and asked, "How is that affected if someone has two phone numbers?"
I'm not sure why the first item reminded me of the second but it did.