Found a factor? Enshrine, embalm and entomb it here! (RU "Выкрасить и выбросить"))

[Luminescence]

10404679: 118793848017180226139209650887 (30 digits, 96.584 bits)

This looks like any old factor... until you take a look at the effort required for this one. Normal P-1 is at 1,069.7 GHz-days and the min. bounds are B1=597,137 and B2=22,193,557,699

Bless version 30.8

[Xyzzy]

10713539

M10713539 has a factor: 9646618965808297396650789217449140593554849484807561 (P-1, B1=3000000, B2=21676825170)

7259945416488565152965177 × 1328745384765454647667709393

[bur]

It was suggested that ECM often makes more sense on those smaller Mersenne than P-1, and yes, there are a lot of low-hanging fruits with t35 done only partially. 1500 B1=1M curves on a 10 core take about 1.5 days and you can be fairly certain you won't miss any factor < 35 digits with that.

First hit:

M177949
Factor: 33673305014952064901960880605783657 (35 digits)

ECM B1=1000000, B2=167000000, Sigma=3976350787451175
k = 2^2 × 7 × 113 × 29903617016456689669335223 (boom, take that, P-1)

Group order:
2^4 × 3 × 251 × 3319 × 26111 × 111767 × 477073 × 741043 × 816203

Don't take this too serious, I did a lot of P-1 and even P+1 and I definitely get the lottery appeal of it with the chance to score big... :)

[petrw1]

Magic_8_Ball	20824319	NF-PM1	2022-01-21 14:35	0.0	B1=800000, B2=288897180	19.4015
Magic_8_Ball	20824147	F-PM1	2022-01-21 14:17	0.0	Factor: 495235256819022693269729 / (P-1, B1=800000, B2=288897180)	19.4015
Magic_8_Ball	20823619	F-PM1	2022-01-21 13:58	0.0	Factor: 25548786609611112273299959 / (P-1, B1=800000, B2=288897180)	19.4015
Magic_8_Ball	20820379	F-PM1	2022-01-21 13:40	0.0	Factor: 1046110442462024597648707729 / (P-1, B1=800000, B2=288897180)	19.4015
Magic_8_Ball	20818361	NF-PM1	2022-01-21 13:21	0.0	B1=800000, B2=288897180	19.4015

[Flaukrotist]

M8180143 has a 210.388-bit (64-digit) composite (P25+P39) factor: 2153365510583437050044092603818787130235731554764189688651981753 (P-1,B1=1500000,B2=800578350)

Yeah, my first double factor in one P-1 attempt. And it includes the largest factor, I found so far (#172 in the Top P-1 factor list).

[Jan S]

104297 B1=3000000, B2=447000000, curve 244

33730663290433956450015516054234200283383287

144.597 bits

[firejuggler]

M14691419 has a 148.225-bit (45-digit) composite (P23+P23) factor: 416943345784701035645026212406037518765877617 (P-1,B1=2100000,B2=534604980)


both are 74 bits

[bur]

M21013
Factor: 262993879056590526599462437387619513220841 (42 digits, 137.6 bits)
B1=3000000, B2=528000000, Sigma=6108330422011107

Group order = 2^2 x 3^5 x 11 x 263 x 643 x 19157 x 20071 x 63331 x 147881 x 652601 x 61893779

k = 2^2 x 3 x 5 x 59 x 242399 x 7292786486304502390480104379

It's the third factor of M21013 (1.56%), remaining co-factor is composite. That factor could have quite likely been found with B1=1M already.

[Zhangrc]

Simon Josefsson has found a factor (7th biggest!)
M108366469 has a factor: 21806524243495451887372970600275462563390077239
(153.933 bits)
Congratulations!

[chalsall]

You have to love statistics...

gpu72ng 11757341        F-PM1   2022-02-03 00:05        6.4     Factor: 18209030934069669978769 / (P-1, B1=2000000, B2=496384980)       18.6152
gpu72   11765911        F-PM1   2022-02-02 23:09        4.3     Factor: 813514493428352514799942217 / (P-1, B1=2000000, B2=496384980)   18.6152
gpu72ng 11757293        F-PM1   2022-02-02 23:03        6.3     Factor: 287095610823108514130103097 / (P-1, B1=2000000, B2=496384980)   18.6152

[bur]

M22621 has a third factor:

140986430775391680242875594970278954759 (39 digits, 126.7 bits)
ECM,  B1=3M, B2=321M, Sigma=3634941837045978
k = 3^3 × 71 × 31481 × 317371 × 5654288209 × 28775289833

I had trouble with the group order though, it had 17 and 18 digits factors which doesn't agree with the B1/B2 bounds. Switching to parameter=1 didn't help. Does anyone know what I did wrong?