20070707, 13:19  #1 
"Jacob"
Sep 2006
Brussels, Belgium
11100010100_{2} Posts 
Not quite a PrimeNet P1 record
I had the pleasure today, after a very long P1 dry spell, of finding a big factor with Prime95 : 784897778891064591942839363373697049558744749633 (159 bits and 48 digits) is a factor of M39122179.
It is the 7th largest factor in the PrimeNet tables, the bigger factors where found for very small exponents : Code:
Exponent Places Factor 727 98 17606291711815434037934881872331611670777491166445300472749449436575622328171096762265466521858927 523 69 160188778313202118610543685368878688932828701136501444932217468039063 751 66 227640245125324450927745881868402667694620457976381782672549806487 809 61 4148386731260605647525186547488842396461625774241327567978137 997 57 167560816514084819488737767976263150405095191554732902607 971 53 23917104973173909566916321016011885041962486321502513 39122179 48 784897778891064591942839363373697049558744749633 3343 47 21395366139013330348249888032891790630577329313 2683 46 3019483344963149568756116899590804134821111103 4177 45 467039490551109991900169555492443530235814719 17504141 45 426315489966437174530195419710289226952407399 The computer I did it on (Quad 6700, 64 bits OS, 4GB of memory) earns 0,307 P90 CPU years a day per core doing LL work, 0,137 doing trial factoring and 0,009 doing P1 work. Actually that last figure should be someting like 0,068 since P1 factoring slows the other cores... Credit earning is not a reason to do P1 work. Last fiddled with by S485122 on 20070707 at 14:18 Reason: I was truncating the factors. 
20070707, 14:46  #2 
Aug 2002
Buenos Aires, Argentina
1,447 Posts 
It appears that you found two prime factors of M39122179 because
784897778891064591942839363373697049558744749633 = 26207295509565505207993 x 29949590891764532677185481 
20070707, 15:38  #3  
"Jacob"
Sep 2006
Brussels, Belgium
2^{2}×3×151 Posts 
Quote:
Anyway after spending 44 core days on 35 exponents in P1 stage 1 and 2 without success, I am still satisfied. So far I did a total of 88 P1 and four times the program found a factor. 

20070707, 16:29  #4 
Aug 2002
Buenos Aires, Argentina
1,447 Posts 
The lowest prime factor has 75 bits so you would not have found it without p1.

20070906, 19:43  #5  
Jun 2003
7·167 Posts 
Quote:
Rather, what happened was that in this instance there were two prime factors that were ksmooth to the bounds of your P1 test: 262072955095655052079931 = 2^3 . 3 . 7 . 43 . 150107 . 617761 . 39122179 299495908917645326771854811 = 2^3 . 3 . 5 . 173 . 1861 . 2087 . 9494491 . 39122179 In this situation, the P1 test returns the product of the factors, an interesting outcome, but by no means exceptional, and certainly not recordbreaking. Last fiddled with by Mr. P1 on 20070906 at 19:53 

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