Largest known probable prime cofactors of Primorial ±1  (proper divisor of p# ±1 with p prime and > 10343)

 Cofactor

 Digits

 When

 (136777# -1)/8823581477

 59254  

 05/2006  

 (97127# -1)/338843573

 42056

 04/2006

 (95617# +1)/3731593

 41415

 04/2006

 (79273# +1)/14236619

 34255

 04/2005

 (35099# +1)/18274679

 15156

 04/2005

 (25087# -1)/(32503 . 223753)    

 10798

 04/2005

 (20173# -1)/3433327

 8681

 02/2005

 (17713# +1)/181957

 7622

 01/2005

 (16831# +1)/42012052913

 7231

 01/2005

 (15991# +1)/9604637744183

 6887

 01/2005

 (15401# -1)/952843

 6634

 12/2004


MultiSieve (written by Mark Rodenkirch) was used to find the factors < 234
GMP-ECM was used to find the factors 42012052913 and 9604637744183

All 11 probable prime cofactors have passed a Miller-Rabin primality test in 10 randomly chosen bases (ispseudoprime test in PARI/GP). The 6 largest probable prime cofactors on this page are listed on Henri Lifchitz's Top 10000 PRPs page: p# +1 and p# -1. All factors on this page were found by me.


p# ±1 for p = 2293 to 10343
p# ±1 for p = 607 to 2287
p# ±1 for p = 2 to 601: Hisanori Mishima's Primorial ±1 Factorizations: p# +1 and p# -1
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Last updated on February 10, 2007
Donovan Johnson