Prime95 version 28 released! Faster on Intel's latest CPUs!
June 1, 2014 — Version 28 is now available for download. The FFT assembly code
has been optimized to use Intel's fused multiply-add instructions on Intel's Haswell CPUs (Core i3/i5/i7-4xxx models).
Haswell users should see a decent performance increase. Sandy Bridge and Ivy Bridge users may also see a small
speed boost due to some memory bandwidth optimizations.
To upgrade, simply exit Prime95, download the new version, and unzip the new version replacing the old version.
New Assignment and Recycling Rules
February 2014 — Since 2008, GIMPS has given users one year to complete assignments.
This rule has not been enforced. This has held up completing milestones
as some assignments did not complete even after several years.
During February 2014, new assignment and
recycling policies were put in place to help GIMPS make steady progress on milestones
by detecting assignments that are proceeding extremely slowly or not at all.
This affects users in two ways:
- When they occasionally become available, if you want to test the
smallest exponents you'll need to sign up on the
assignment rules page and be aware of the shorter timeline for returning
- Your computers that are proven producers will have 8 or 9 months to
complete assignments. Your slower computers and computers with a limited track record
will still have a full year to complete their assignments.
Users testing 100 million digit numbers are not affected by these new
rules. Assignments made prior to March 1, 2014 will be given a year, as promised, to
complete (plus a grace period if the assignment is close to complete).
M(30402457) proven to be 43rd Mersenne Prime
February 23, 2014 — More than 8 years after discovering M(30402457), GIMPS has finished checking and
double-checking every smaller Mersenne number. With no new primes found that are smaller
than M(30402457), the "43rd known Mersenne
prime" can now be called the "43rd Mersenne prime". Congratulations and thanks to all the
GIMPS members that perform this somewhat less glamorous double-checking work.
Largest Known Prime, 48th Known Mersenne Prime Found!!
January 25th, 2013 — Prolific GIMPS contributor Dr. Curtis Cooper
discovered the 48th known Mersenne prime, 257,885,161-1, a
17,425,170 digit number. This find shatters the previous record prime number of 12,978,189 digits, also a GIMPS prime, discovered over 4 years
ago. The discovery is eligible for a $3,000 GIMPS research discovery
Dr. Cooper is a professor at the University of Central Missouri. This is the third record prime for Dr. Cooper and
his University. Their first record prime was discovered in 2005, eclipsed by their second record
in 2006. Computers at UCLA broke that record in 2008. UCLA held the record until Dr. Cooper and
the University of Central Missouri reclaimed the world record with this discovery.
While Dr. Cooper's computer found the record prime, the discovery would not
have been possible without all the GIMPS volunteers that sifted through numerous non-prime
candidates. GIMPS founder George Woltman and PrimeNet creator Scott Kurowski thank and
congratulate all the GIMPS members that made this discovery possible.
Mersenne primes are extremely rare, only 48 are known. GIMPS, founded in 1996,
has discovered the last 14 Mersenne primes. Mersenne primes were named for the French monk
Mersenne, who studied these numbers more than 350 years ago. Chris Caldwell maintains an
authoritative web site on the history of
Mersenne primes as well as the largest known primes.
The primality proof took 39 days of non-stop computing on one of the University
of Central Missouri's PCs. To establish there were no errors during the proof, the new prime was
independently verified using different programs running on different hardware. Jerry Hallett
verified the prime using CUDALucas running on a NVidia GPU in
3.6 days. Dr. Jeff Gilchrist verified the find using the standard GIMPS software on an Intel i7
CPU in 4.5 days. Finally, Serge Batalov ran Ernst Mayer's MLucas software on a 32-core server in 6 days
(resource donated by Novartis IT group) to verify the new
You can read a little more in the short press release.
M(25964951) proven to be 42nd Mersenne Prime
December 20, 2012 — One year after proving the 41st Mersenne prime, GIMPS
finished double-checking every smaller Mersenne number than M(25964951) -- proving that this prime is indeed the 42nd Mersenne
prime. There are 47 known Mersenne primes. Mersenne primes are sometimes
discovered out-of-order. It is not yet known if there is an undiscovered Mersenne prime between
M(25964951) and the next largest known Mersenne prime,
M(30402457). Here is a list of all GIMPS milestones and our progress toward future ones. Congratulations and
thanks to all the GIMPS members that contributed to this important double-checking
Prime95 version 27 released! Faster on Intel's newer CPUs!
May 15, 2012 — You may download version
27 now. The FFT assembly code has been rewritten for better speed on Intel's newer CPUs
supporting AVX instructions. Sandy Bridge and Ivy Bridge CPUs (Core i3/i5/i7-2xxx and 3xxx
models) should see a huge performance increase. To upgrade, simply exit Prime95, download the new
version, and unzip the new version replacing the old version.
GIMPS now accepting donations
GIMPS is now accepting
donations to help fund server upgrades and future Mersenne Prime prize awards. Donations are
tax-deductible in the U.S.
October 14, 2009 — Could YOU be the next person to
discover a new Mersenne prime and win a cash research
Frontier Foundation awarded GIMPS the $100,000 Cooperative Computing Award for the
August 23rd, 2008 discovery of the 45th known Mersenne prime ("M45") 243,112,609-1, a mammoth
12,978,189 digit number, found on a University of California
Los Angeles (UCLA) computer in the GIMPS PrimeNet network, after GIMPS met every requirement for the $100,000 award for discovery of the first 10 million digit
As promised, GIMPS gave $50,000 of the EFF award
to the UCLA Department of Mathematics, where Edson Smith was responsible for installing and
maintaining the GIMPS software on their computers. Another $25,000 has been donated to a
math-related charity selected by GIMPS founder George Woltman. The remaining $25,000 has
been paid in GIMPS Mersenne Prime Research Discovery Awards to Odd
Magnar Strindmo for his discovery of M47, Hans-Michael
Elvenich for M46, the University of Central Missouri
(M44 and M43), Dr.
Martin Nowak (M42), Josh Findley (M41), Michael Shafer and his selected charity (M40) and Michael Cameron (M39).
Chris Caldwell maintains an excellent web site on
prime numbers. See his page on Mersenne
Primes and their history. GIMPS has found 13 of the 47 Mersenne
primes ever found during its 13 year
Mersenne Wiki Created — From the good folks
that brought you the Mersenne Forums comes the
Mersenne Wiki. Browse the Wiki to learn more about
GIMPS and Mersenne Primes.
GIMPS forums — Here you can chat with fellow GIMPS members, get help with
installation questions, learn more about how GIMPS works, etc.
Make Math History!!
You could discover one of the most coveted finds
in all of Mathematics - a new Mersenne prime number. We've found fourteen already. Join in on this fun, yet serious
research project. All you need is a personal computer, patience, and a lot of
In addition to the joy of making a mathematical
discovery, you could win a (USD) $3,000 cash GIMPS Research Discovery
Award for each Mersenne prime discovered, and the Electronic
Frontier Foundation is offering a $150,000 award
to the first person or group to discover a 100 million digit prime number! See how GIMPS will distribute this award if we are lucky enough to find the winning
100 million digit prime.
What are Mersenne primes and why do we search for them?
Prime numbers have long fascinated amateur and
professional mathematicians. An integer greater than one is called a prime number if its only
divisors are one and itself. The first prime numbers are 2, 3, 5, 7, 11, etc. For example, the
number 10 is not prime because it is divisible by 2 and 5. A Mersenne prime is a prime of the
form 2P-1. The first Mersenne primes are 3, 7, 31, 127 (corresponding to P = 2, 3, 5,
7). There are only 46 known Mersenne primes.
GIMPS, the Great Internet Mersenne Prime Search,
was formed in January 1996 to discover new world-record-size Mersenne primes. GIMPS harnesses the
power of thousands of small computers like yours to search for these "needles in a
Most GIMPS members join the search for the thrill
of possibly discovering a record-setting, rare, and historic new Mersenne prime. Of course, there
are many other
Last Updated June 1, 2014