Largest known probable prime Fibonacci Cofactors  (proper divisor of a Fibonacci number with a prime index)

 Cofactor

 Digits

 When

 U(348307)/(1393229 . 14759160817)

 72776  

 07/2007  

 U(228223)/(1369337 . 89717648662417)

 47676  

 05/2007  

 U(208519)/(417037 . 337800781)

 43564  

 05/2007  

 U(179689)/359377

 37547  

 11/2005  

 U(138449)/722703781

 28925

 09/2005

 U(117167)/17658707237

 24476

 08/2005

 U(71983)/(5614673 . 363946049)

 15028

 06/2005

 U(69239)/1384781

 14464

 08/2004

 U(66947)/(130011073 . 1211874593 . 77572426157 . 1021533561481)    

 13951

 06/2005

 U(42043)/1681721

 8780

 08/2004

 U(37987)/(16117960073 . 94533840409 . 1202815961509)

 7906

 05/2005

 U(37217)/4466041

 7771

 08/2004


All 12 probable prime cofactors have passed a Miller-Rabin primality test in 10 randomly chosen bases (ispseudoprime test in PARI/GP). The 9 largest probable prime cofactors on this page are listed on Henri Lifchitz's Top 10000 PRPs page. Click here to view. All probable prime cofactors on this page were found by me except U(117167)/17658707237 was found by Jens Kruse Andersen.


Blair Kelly's Fibonacci and Lucas Factorizations
20 largest known prime Fibonacci cofactors (The Prime Pages)
Biography of Fibonacci (Leonardo of Pisa)
Main page


Last updated on July 12, 2007
Donovan Johnson