1 261 963 Exponent Status

Great Internet Mersenne Prime Search
GIMPS
Finding World Record Primes Since 1996

PrimeNet Exponent Status

M_n

Status

Details

Composite, with 1 known prime factor. Cofactor is composite.

Factored

Factor	Digits	Bits	Date
1562497500758296835611884802575769	34	110.3	2015-02-06 11:29:16

ECM

Digits	B1	Curves
25	50000	280 / 280
30	250000	100 / 640

Estimated T-Level: 25.8 ⓘ

TF below 2^81 is very unlikely to find new factors due to ECM effort.

Status	Date	User	Residue	Shift
Verified (Factored)		Ars Technica Team Prime Rib	3521926B7722437C	0
Verified (Factored)		The Grebelius Family	3521926B7722437C	0
Verified (Factored)		Simon Burge	3521926B7722437C	0

Status	Date	User	Residue	Shift	Type	Base
Verified (Factored)	2025-09-01	Kriesel	0D38DA285751B9A4	0	1	3

Status	Date	User	Residue	Number of known factors	Shift	Type	Base
Verified	2017-09-29	Oliver Kruse	DCA82C87E5AEFDF1	1	0	1	3
Verified	2017-10-21	kkmrkkblmbrbk	DCA82C87E5AEFDF1	1	953463	1	3

P-1 factors

Date	Factor	B1	B2
2015-02-06	1562497500758296835611884802575769	4218475	156083565

History

Date	User	Type	Result
2025-09-02	takahashi	CERT	PRP Certification CERT proof power = 6 Proof certified good
2025-09-01	Kriesel	C-PRP	0D38DA285751B9A4 PRP proof power = 6 PRP: Verified (Factored) Proof certified good
2022-03-07	LordJulius	NF	no factor from 2^58 to 2^60
2017-10-21	kkmrkkblmbrbk	C-PRP	M1261963/1562497500758296835611884802575769 : DCA82C87E5AEFDF1 PRP: Verified PRP without proof (not generated)
2017-09-29	Oliver Kruse	C-PRP	M1261963/1562497500758296835611884802575769 : DCA82C87E5AEFDF1 PRP: Verified PRP without proof (not generated)
2015-02-06	mikr	F-PM1	Factor: 1562497500758296835611884802575769 / (P-1, B1=4218475, B2=156083565, E=12)
2014-09-29	Joss	NF-PM1	B1=250860
2012-10-11	dbaugh	NF	no factor from 2^62 to 2^63
2011-05-09	megavink	NF	no factor from 2^61 to 2^62
2009-02-14	Sturle Sunde	NF	no factor from 2^60 to 2^61