When was the last prime number discovered?

Question

By last, I mean the most recently discovered prime number. What was the length of time between the discovery of the last two prime numbers?

Answer 1

See the page The Largest Known Primes--A Summary by Chris K. Caldwell

(A historic Prime Page resource since 1994!)

Last modified: 16:20:41 Monday August 29 2011 UTC.

In particular this subpage and this one.

Answer 2

Apart from very large "special" primes, it is also possible to make/construct large "certified" primes, using the Pocklington-Lehmer criterion. That is, although one must "search" ("randomly") for primes readily certifiable, once they are found one can "attach" to them a small amount of data that anyone interested could use to verify their primality (via Pocklington-Lehmer, for example). In particular, although the search is obviously probabilistic, the certification is not.