2+(4k)

2^1256+1

Open composite · C312

NFS Planning

GNFS Murphy estimate: 1.79e-21
SNFS Murphy score: 1.15e-17
Preferred method: SNFS
SNFS possible: Yes
SNFS degree: 7
SNFS skew: 1.06300

Identifiers

Target expression: 2^1256+1
Target link: FactorDB page
Target ID: 1000000000012151280
Target changed: -
Parent query: Same as target
Parent ID: -
Cofactor token: C312
Imported: Jun 03, 2026, 04:30 PM UTC

Raw pmain126 Factorization

(8) 2024020769633129857.4914060388472339641563884985215767969679703073.C312

SNFS Polynomial

Polynomial

Degree: 7
Murphy: 1.15e-17
Skew: 1.06300
Selected: Best

n: 485384581601104033021963601536371733500477368689714096643692334981803648515088687244967611405970428552435133343799982444554562116268814393776619811822134010100299946507012731918453591771616673342176345188354438558156411154194276489511265494315665566973935408754134969855895492923754317311753702267550504538390881
# 2^1256+1, difficulty: 378.09, skewness: 1.35
# cost: 4.45653e+22, est. time: 21221571.46 GHz days (not accurate yet!)
# Optimized skew: 1.06300 Murphy: 1.15e-17
skew: 1.06300
c7: 1
c0: 8
Y1: -766247770432944429179173513575154591809369561091801088
Y0: 1
type: snfs