We are glad to announce that
MC7331 = (2^7331-1)/458072843161
is prime. This number has 2196 decimal digits and is the new
record for general purpose primality proving (as far as we know).
Indeed, the former record was hold by the first author for a while
(1510 digits and later 1549 in 1997), succeeding to the second author who had
been holding it with 1505 digits since 1992. Note that all of these
records were done with the new version of ECPP. Time for this number was 1
month of CPU on an Alpha 400 MHz.
The certificate for MC7331 can also be found here.
For more Mersenne factorizations, see here.