6 221 Exponent Status

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

PrimeNet Exponent Status

M_n

Details

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

Trial Factored to 2⁶⁸

TF target 2⁴⁴

Assignments

Assigned	User	Work Type	Stage	% Done	Updated	Est Complete	Expired
2026-02-21	Graham Barnes	ECM	C54S2	28.95 %	2026-02-23	2026-02-23

Factored

Factor	Digits	Bits	Date
555190029021937960947814145119	30	98.8	old

ECM

Digits	B1	Curves
25	50000	280 / 280
30	250000	640 / 640
35	1000000	1566 / 1566
40	3000000	4588 / 4588
45	11000000	9201 / 9201
50	44000000	3289 / 16550

Estimated T-Level: 46.0 ⓘ

TF below 2^148 is very unlikely to find new factors due to ECM effort.

Status	Proof	Date	User	Residue	Number of known factors	Shift	Type	Base
Verified	No proof (small exponent)	2017-09-21	Oliver Kruse	6D965766ADC67B2E	1	0	1	3
Verified	No proof (small exponent)	2017-10-12	kkmrkkblmbrbk	6D965766ADC67B2E	1	2384	1	3
Verified	No proof (small exponent)	2020-04-17	Oliver Kruse	14EADB5C389D4D02	1	5774	5	3
Verified	No proof (small exponent)	2024-02-03	Wentao Huang	14EADB5C389D4D02	1	1171	5	3

History

Date	User	Type	Result
2025-03-18	masser	NF-PP1	Start=125/13, B1=1000000000, B2=999000000000
2025-03-10	masser	NF-PP1	Start=6/5, B1=1000000000, B2=999000000000
2025-03-01	masser	NF-PP1	Start=2/7, B1=1000000000, B2=999000000000
2024-02-03	Wentao Huang	C-PRP	M6221/555190029021937960947814145119 : 14EADB5C389D4D02
2023-07-31	-anonymous-	NF-PM1	B1=40000000000, B2=169615672618692300
2021-08-01	ViliamF	NF-PM1	B1=500000000, B2=90500000000
2020-04-17	Oliver Kruse	C-PRP	M6221/555190029021937960947814145119 : 14EADB5C389D4D02
2017-10-12	kkmrkkblmbrbk	C-PRP	M6221/555190029021937960947814145119 : 6D965766ADC67B2E
2017-09-21	Oliver Kruse	C-PRP	M6221/555190029021937960947814145119 : 6D965766ADC67B2E
2017-09-21	Oliver Kruse	C-PRP	M6221/555190029021937960947814145119 : 6D965766ADC67B2E
1999-12-30	-anonymous-	NF	no factor TF: 53-54
1999-09-22	-anonymous-	NF	no factor TF: 52-53