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Old 2004-04-08, 06:45   #1
dave_0273
 
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Default P-1 stage 2 factor

I just beat my own personal record and just found a 43 digit factor during stage 2 of p-1 factoring. My previous record was 42 digits.

P-1 found a factor in stage #2, B1=70000, B2=1277500.
UID: dave_0273/buffy, M12215821 has a factor: 2855451057157704997579326497626590663028969

Assuming that I did the calculation correct, this is a 142 bit factor.

I am interested to know if anyone has found a bigger factor using p-1. Also, I was wondering if this number is prime, I highly doubt that it is though.

Last fiddled with by dave_0273 on 2004-04-08 at 07:15
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Old 2004-04-08, 07:38   #2
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Unfortunately it's not a prime :

Code:
2855451057157704997579326497626590663028969 =
896774094182730749591 * 3184136423744490284159
So you found two factors in time. You can check this for example with a UBASIC program like ECMX.
A list with p-1 records you can find in the ECMnet pages : http://www.loria.fr/~zimmerma/records/Pminus1.html
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Old 2004-04-09, 02:41   #3
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I just beat my own record again. Interesting that I beat it just the next day. Anyways, here is the factor....

P-1 found a factor in stage #2, B1=70000, B2=1312500.
UID: dave_0273/faith, M12223199 has a factor: 264230314763760208834215981504580626343342447

It is 45 digits and weighs in at 148 bits. Could someone check for me to see if it is prime please??

Last fiddled with by dave_0273 on 2004-04-09 at 02:47
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Old 2004-04-09, 02:50   #4
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Quote:
Originally Posted by dave_0273
It is 45 digits and weighs in at 148 bits. Could someone check for me to see if it is prime please??
It's not: 264230314763760208834215981504580626343342447 = 46673864303955381847 x 5661205017073505552389801

You can check them yourself at http://www.alpertron.com.ar/ECM.HTM
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Old 2004-04-09, 03:01   #5
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Thanks for that link.
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Old 2004-04-15, 16:41   #6
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Well done Dave, you qualify for that list.

I'm just not in the same ball park - my largest is 25digits: 3392287301461488893415377 for M13127581. But hey it's prime :)

Is there a way to look up the data files to see if anyone else has anything bigger?

-- Craig
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Old 2004-04-15, 20:31   #7
Prime95
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These are the 35 digit and longer factors found with prime95:

17504141 45.00 426315489966437174530195419710289226952407399
1026199 41.00 99986711862609678639226074113089334488633
14334623 39.00 563796628294674772855559264041716715663
23343809 39.00 126200820168972868753938399731010991289
15864539 37.00 5811726848289439035828246985293098183
20396191 36.00 275806877795314616777110237874197111
5480471 35.00 87590114272360866473519508282751337
13187813 35.00 63113922700063643342764849026462401
1018697 35.00 51776547638454015479754532135290881
18965599 35.00 34488602653675602192712514732427431
16026793 35.00 19929728012623917458862281965016471
20092067 35.00 13168424217984320584506969049382921
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Old 2004-04-15, 21:23   #8
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What about

6659 42.00 226211124686120782835233945344253671049543
27691 37.00 1734072082042172647364731231822850071

Both are 'smooth' enough for Prime95.
(found in an old list created by Andy Steward)
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Old 2004-04-15, 22:02   #9
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43 and 45 would both put you on the top 10 list.
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Old 2004-06-07, 14:50   #10
dave_0273
 
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It doesn't beat my personal best, but here is a 43 digit factor

UID: dave_0273/buffy, M12889889 has a factor: 2975472867644373392513490171544511832022967

Unfortunately, it isn't prime

2975472867644373392513490171544511832022967 = 26296325190058 952183 x 113151660779173033002049

Still, I thought that it was worth mentioning. It is a 142 bit factor.
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Old 2004-06-07, 21:27   #11
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Quote:
Originally Posted by dave_0273
It doesn't beat my personal best, but here is a 43 digit factor

UID: dave_0273/buffy, M12889889 has a factor: 2975472867644373392513490171544511832022967

Unfortunately, it isn't prime

2975472867644373392513490171544511832022967 = 26296325190058 952183 x 113151660779173033002049

Still, I thought that it was worth mentioning. It is a 142 bit factor.
How do you choose Mesennes to P-1 factoring?

Did those numbers already have their LL test (I guess so)?

Luigi
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