"the number was factored by I.Popovyan from MSU, Russia and A. Timofeev from CWI, Netherlands and took a few months of a pure computer time on various parallel systems in both MSU and CWI" (mersenneforum).
The polynomial they used is (information generated by CADO-NFS),
c5: 40208599020
c4: -1373979915646426
c3: -18783091380980602091391
c2: 32414999912320727344430346523
c1: -375830488267489810578184841744243639
c0: 348578818479643113591848726218653819076813
Y1: 127570152207571988302487
Y0: -543540225411856459303967064165519554
# lognorm 59.40, alpha -5.64, 1 rroots
# Murphy's E(Bf=10000000,Bg=5000000,area=1.00e+16)=1.55e-14 (CADO-NFS)
This polynomial seems to be the best one along its neighbour rotation space (10000x50000000000) by rootsieve in CADO-NFS.
n: 1907556405060696491061450432646028861081179759533
1844606479756223189150255871841757540549761551215932
9349226046415263009323850924660320741712472612158085
8185985938946945490481721756401423481
c5: 255190140
c4: -47260029758132866
c3: 11100977719061907146275874
c2: 199076980463854285552426407486731
c1: -5248708483538855234690491711962684053766
c0: 5447894568502905764476664798517077173925915847
Y1: 2642639550249635903
Y0: -1495280603333333570159597505117010240
# lognorm 63.72, alpha -8.81, 3 rroots
# Murphy's E(Bf=10000000,Bg=5000000,area=1.00e+16)=1.30e-14 (CADO-NFS)
# norm 8.395467e-19 alpha -8.805648 e 1.465e-14 rroots 3 (msieve)
rlim: 100000000
alim: 200000000
lpbr: 32
lpba: 32
mfbr: 64
mfba: 96
rlambda: 2.4
alambda: 3.4