20211226, 13:37  #1 
Aug 2002
Buenos Aires, Argentina
1,447 Posts 
New Mersenne number with 12 known prime factors
Up to now there were only 4 Mersenne numbers with 11 known prime factors. They are M7 508 981, M9 100 919, M3 356 318 939 and M3 930 621 659.
Today I added another Mersenne number to this list: using the algorithm P1 with B1 = B2 = 1M, I found the eleventh prime factor known of M726 064 763: 10702385060027676180416983. Last fiddled with by alpertron on 20211226 at 14:31 Reason: Added links to mersenne.ca 
20211227, 09:34  #2 
Dec 2016
170_{8} Posts 
Awesome! Until a few days ago, there were only 3 such numbers, and all their factors had been found in 2014 or earlier. And now we have two more within two weeks! Are you still going to do P1 stage 2? If we get very lucky, there might be a 12th factor.

20211227, 12:50  #3 
Aug 2002
Buenos Aires, Argentina
1,447 Posts 
Unfortunately there is bug in 30.8 build 6 when running step 2.
I used the following line in worktodo.txt: Code:
Pminus1=1,2,726064763,1,1000000,10000000,"1452129527,1023751315831,1030134877226297,7106729160891631,7236079050549607,12965740712769703,37915764094923857,7565365825277361223,34153055801363324180057,490609746862823011746041,10702385060027676180416983" I reserved 20 GB for Prime95. 
20211227, 14:49  #4 
Einyen
Dec 2003
Denmark
CF1_{16} Posts 
Did it really use B2=10M or did it choose it's own value? If it did not use 10M then try Pminus1BestB2=0 in prime.txt.
Otherwise it probably needs more than 20GB RAM. 
20211227, 15:07  #5 
Aug 2002
Buenos Aires, Argentina
1,447 Posts 
I really used B2 = 10M in this test.
It is strange that the step 2 has completed except for the final GCD. But the GCD works OK because it found the prime factor in step 1. I had the same problem some days ago when I selected B1 = 100K, B2 = 0 (so Prime95 selected automatically B2 = 9*B1 = 900K. 
20211228, 13:10  #6 
Jun 2003
2×2,683 Posts 
And Mike's factor makes it 12.

20211228, 14:16  #7 
Aug 2002
Buenos Aires, Argentina
10110100111_{2} Posts 
Yes, that's a "world record". There is a nonnegligible probability of finding the 13th known prime number by increasing B2 to 200M (but this would require a lot of RAM).
Last fiddled with by alpertron on 20211228 at 14:29 
20211228, 17:32  #8 
Dec 2016
1111000_{2} Posts 
That was super lucky! The first time since 2014 that a new record gets set. Congrats to Alpertron and Xyzzy!
And we can actually try our luck a bit more: The P1 can still be extended and TF could be done for some more bit levels. I, for one, will give P+1 factoring a chance, using nth_run=1. If someone with plenty of RAM (I'm allowing 90GB for stage 2) wants to try nth_run=2, use Code:
Pplus1=N/A,1,2,726064763,1,1000000,10000000,2,82,"1452129527,1023751315831,1030134877226297,7106729160891631,7236079050549607,12965740712769703,37915764094923857,7565365825277361223,34153055801363324180057,490609746862823011746041,7170112396664438582504527,10702385060027676180416983" 
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