Mersenne factorization

Continuing this project with larger Mersenne primes.

The recent factorization of 2^1101+1 by Silverman (page 108, entry 5623 of the Cunningham Project) gives us

? isprime(2^2203-1)

%59 = 1

? print(factor(2^2203-2))

[2, 1; 3, 2; 7, 1; 2203, 1; 12479, 1; 19819, 1; 28627, 1; 79273, 1; 51791041, 1; 78138581882953, 1; 146264881313513, 1; 20837062885084633147, 1; 258977744356523549983, 1; 301311116540899114446723859201, 1; 883533090360873723903538281367, 1; 460233616861852066165180033789571, 1; 1636198597169607245088331633873083979, 1; 19755740081951910036006278827509875120092863638283602681, 1; 79073321945266228838262115990524608069915168947411523193620486700648001, 1; 13307293644989926855503183079276784290565688582692135767130945147226822516757076633431114901443896343698334635540215594678754538286654095364149897, 1; 711718443060888357455104383759579899185453159253854240850359788937324328008225366876777905349283339583535597500393178373807851032788989008946432082299780350922963303, 1]

After 232125395706826190501, leaves us challenges:

c105 has factor 1165410983472064229956077783033756619354709 (via ECM) and the larger one falls to 60716055995924620572719451834239 followed by 115092709908691724294367540635071

? ispseudoprime(2^3217-1)

%5 = 1

? print(factor(2^3217-2))

[2, 1; 3, 2; 5, 1; 7, 1; 13, 1; 17, 1; 97, 1; 241, 1; 257, 1; 269, 1; 673, 1; 1609, 1; 2011, 1; 3217, 1; 4289, 1; 9649, 1; 10453, 1; 22111, 1; 75041, 1; 132661, 1; 192961, 1; 6324667, 1; 7327657, 1; 15152453, 1; 42875177, 1; 58846369, 1; 193707721, 1; 209898673, 1; 214473433, 1; 2559066073, 1; 71848008781, 1; 175132692529, 1; 761838257287, 1; 6713103182899, 1; 6925799047681, 1; 9739278030221, 1; 21402380066017, 1; 333808138537249, 1; 29493338799546784993, 1; 59151549118532676874448563, 1; 36360649135813582804156044289, 1; 133304540580175280319733184641, 1; 15704900959651293774270521395753, 1; 87449423397425857942678833145441, 1; 22845623493785363787359045076091739713, 1; 311532723090035002320027134588551176448471666435989092897, 1; 1113767094422199900605896348724787045161997478687751948513969, 1; 163309771760986620014536331036091658009630202169109324871656084993557377301963746856626689, 1; 655065662598900362767578455116791254630312910908827632908253411351301525671199788835777321465298977, 1; 740887329174524327455005745661306728131406389630924979029857723424410009046767537884650900512703207784774794207122435593649368728149684897691507733781127878673273900985500310966336106589083780932968731424118506572640082702736435521, 1]

using http://www.euronet.nl/users/bota/medium-p-even4k.txt (Arjen Bot) for 2^1608+1. This page was found by google searching "58846369" which I found as a factor.

The C187 (after 142724002520786353) is

1068240625262629567200191016033534686294973766625910182558848952050153878490870601823590709054333618002131347133455436225486745521448263699420827688564971719076145154668647793187749244171