For further information on multifactorial primes please see Chris Caldwell's
glossary page on
Multifactorial Primes
This site continues the work
of Ray Ballinger.
The MultiF project's, which started in 2003 aims at finding all primes of the form n!k+/-1 where 2<=k<=25
To participate
MultiF's
position by number of Primes found
MultiF's
position by score for Primes found
07/02/2010 Michael Lau proves 417240!23+1 (digits: 94083) prime
28/01/2010 Matt Mills finishes !23-1 to 230000 finding 9 additional primes including 229345!23-1 (digits: 49125)
18/01/2010 Ken Davis finishes !22-1 to 220000 ==> all types complete up to 10000*type.
07/01/2010 Matt Mills Proves 171232!23-1 (digits: 35733), 172344!23-1 (digits: 35986) and 177871!23-1(digits: 37246) prime
01/01/2010 Matt Mills proves 166332!23-1 (digits: 34619) prime
31/12/2009 Matt Mills proves 200379!23-1 (digits: 42410) prime
23/12/2009 Matt Mills reserves !23-1 type
26/09/2009 Rene Dohmen proves 208502!7+1 (digits 145502) prime (new multifactorial record)
31/08/2009 Rene Dohmen proves 190453!7-1 (digits: 131837) and 206494!7+1 (digits: 143977) prime
14/08/2009 Michael Lau proves 382722!23+1 (digits: 85676) prime
Recent changes are in Red
| Type | nmaxtested |
Digits* |
Searcher | primes |
| n!2+1 | 100000 | 112762 | primes | |
| n!2-1 | 100000 | 93343 | primes | |
| n!3+1 | 100000 | 144697 | primes | |
| n!3-1 | 110000 | 84173 | Andrea Pacini | primes |
| n!4+1 | 120000 | 58508 | Don Routman | primes |
| n!4-1 | 120000 | 51252 | Don Routman | primes |
| n!5+1 | 100000 | 69090 | primes | |
| n!5-1 | 100000 | 77730 | primes | |
| n!6+1 | 100000 | 75339 | primes | |
| n!6-1 | 100000 | 64524 | primes | |
| n!7+1 | 208502 | 145502 | Rene Dohmen | primes |
| n!7-1 | 190453 | 131837 | Rene Dohmen | primes |
| n!8+1 | 140760 | 61535 | Kimmo Herranen | primes |
| n!8-1 | 100000 | 54736 | Kimmo Herranen | primes |
| n!9+1 | 100000 | 46520 | primes | |
| n!9-1 | 100000 | 49304 | primes | |
| n!10+1 | 120000 | 50053 | primes | |
| n!10-1 | 120000 | 50001 | primes | |
| n!11+1 | 275259 | 124096 | Ken Davis | primes |
| n!11-1 | 275259 | 125257 | Ken Davis | primes |
| n!12+1 | 120000 | 43013 | primes | |
| n!12-1 | 120000 | 41435 | primes | |
| n!13+1 | 150000 | 52550 | primes | |
| n!13-1 | 150000 | 52097 | primes | |
| n!14+1 | 145200 | 47569 | primes | |
| n!14-1 | 200000 | 68950 | primes | |
| n!15+1 | 150000 | 43867 | primes | |
| n!15-1 | 150000 | 46186 | primes | |
| n!16+1 | 160000 | 43117 | primes | |
| n!16-1 | 160000 | 45370 | primes | |
| n!17+1 | 170000 | 46924 | primes | |
| n!17-1 | 170000 | 46817 | primes | |
| n!18+1 | 180000 | 46361 | primes | |
| n!18-1 | 180000 | 46900 | primes | |
| n!19+1 | 200000 | 50037 | primes | |
| n!19-1 | 200000 | 49615 | primes | |
| n!20+1 | 200000 | 73102 | Masataka Oita (290700) 250001+ | primes |
| n!20-1 | 200000 | 72521 | Masataka Oita (288574) 250001+ | primes |
| n!21+1 | 212048 | 49402 | Masataka Oita (319773) ? | primes |
| n!21-1 | 210000 | 41387 | primes | |
| n!22+1 | 220000 | 47541 | primes | |
| n!22-1 | 220000 | 43162 | Ken Davis | primes |
| n!23+1 | 417305 | 90783 | Michael Lau | primes |
| n!23-1 | 230000 | 49125 | Matt Mills | primes |
| n!24+1 | 240000 | 47047 | primes | |
| n!24-1 | 240000 | 48575 | primes | |
| n!25+1 | 250000 | 46619 | primes | |
| n!25-1 | 250000 | 47337 | primes | |
| n!+/-1 | 30000+ | +107707
-142891 |
Various | primes |
* Number of digits in the largest known prime of this form
Multifactorial primes of a different flavour n!k+/-2