this is all very cool, but i fail to see the need for prime numbers this large, other than so you can brag about the record to your fellow nerds of course.
(These aren't particularly large for prime numbers. They're big for prime number chains.) Some mathematicians may find this data useful. That's already infinitely more valuable than the results of bitcoin's sha256 / litecoin's scrypt random proof-of-work statements outside of the context of the currency.
good point, however i disagree that they are "infinitely more valuable". XPM(prime) has scientific value(which in my mind is debatable, but then again i'm no mathematician) and sha and scrypt has security(proven until its broken) seems like an apples and oranges argument to me.