The Largest Known Primes
Contents:
- Introduction (What are primes? Who cares?)
- The "Top Ten" Record Primes
- The Complete List of the Largest Known Primes
- Other Sources of Prime Information
- Notation and Definitions
- Euclid's Proof of the Infinitude of Primes
- Comments? Suggestions? New records? New Links?
Related Local Documents:
Note: The most recent version of the Largest
Known Primes home page (this document) can always be found at
http://www.utm.edu/research/primes/largest.html.
Introduction
An integer greater than one is called a prime number if
its only positive divisors (factors) are one and itself. For example,
the prime divisors of 10 are
2 and 5; and the first six primes are 2, 3, 5, 7, 11 and 13. The
Fundamental Theorem of Arithmetic shows that the primes are
the building blocks of the positive integers: every positive integer is a
product of prime numbers in one and only one way, except for the order
of the factors.
The ancient Greeks proved (ca 300 BC)
that there were infinitely many primes and
that they were irregularly spaced (there can be arbitrarily large gaps
between successive primes). On the other hand, in the nineteenth
century it was shown that the number of primes less
than or equal to n approaches
n/(ln n) (as n gets very large);
so a rough estimate for the nth prime is n ln n.
The Sieve of Eratosthenes is still the most efficient way of
finding all very small primes (e.g., those less than 1,000,000).
However, most of the largest primes are found
using special cases of Largrange's Theorem from group theory. See
the separate document
finding primes for more information.
Recently computers and cryptology have given a new emphasis to search for
ever larger primes--at this site we store lists of thousands of these record
breaking primes, all of which have over 1,000 digits! The complete list of
approximately 10,000 primes is available in several
forms below; but first we offer
a few records for your perusal. (See:
notation for an explanation of the symbols
used here; references for a list of
other sources of prime information; and of course,
comments and suggestions
are always requested!)
The problem of distinguishing prime numbers from composite numbers
and of resolving the latter into their prime factors is known to
be one of the most important and useful in arithmetic. It has engaged
the industry and wisdom of ancient and modern geometers to such an
extent that it would be superfluous to discuss the problem at length...
Further, the dignity of the science itself seems to require
that every possible means be explored for the solution
of a problem so elegant and so celebrated. (Karl Friedrich Gauss,
Disquisitiones Arithmeticae, 1801)
Return to table of contents.
The "Top Ten" Record Primes
- The Five Largest Known Primes
- On January 4, 1994 David Slowinski announced on the internet that
he and Paul Gage have found a new record prime: 2^859433-1.
The proof of this 258,716 digit number's primality
(using the traditional
Lucas-Lehmer test) took about 7.2 hours on a Cray C90
super computer. Richard Crandall independently verified
the primality. (The complete decimal expansion of this prime is available
here). The next largest primes and their discoverers are
- 2^756839-1 (227832 digits); Slowinski and Gage, 1992
- 391581*2^216193-1 (65087 digits); Noll and others, 1989
- 2^216091-1 (65050 digits); Slowinski, 1985
- 3*2^157169+1 (47314 digits); Jeffrey Young, 1995 (Fermat F157167
Factor)
- 9*2^149143+1 (44898 digits); Jeffrey Young, 1995
- 9*2^147073+1 (44275 digits); Jeffrey Young, 1995
- 9*2^145247+1 (43725 digits); Jeffrey Young, 1995
- 2^132049-1 (39751 digits); Slowinski, 1983
- 9*2^127003+1 (38233 digits); Jeffrey Young, 1995
(The primes by Jeffrey Young are
from a recent preprint.)
- The Largest Known Twin Primes
- Twin primes are primes of the
form p and p+2, i.e., they differ
by two. It is conjectured, but not yet proven, that there
are infinitely many twin primes (the same is true for all of
the following forms of primes, see conjectures for more information).
- 697053813*2^16352+/-1 (4932 digits); Indlekofer and Ja'rai 1994
- 6797727*2^15328+1/-1 (4622 digits); Tony Forbes
- 1692923232*10^4020+/-1 (4030 digits); Dubner 1993
- 4655478828*10^3429+/-1 (3439 digits); Dubner 1993
- 1706595*2^11235+/-1 (3389 digits); Noll and others 1989
- 459*2^8529+/-1 (2571 digits); Dubner 1993
- The Largest Known Mersenne Primes
- Mersenne primes are primes of the
form 2^p-1. These are the easiest type of number to
check for primality on a binary
computer so they usually are also the largest primes known.
Altogether 33 of these primes are known, but since the region between
the largest two and the previous primes has not been
completely searched we do not know if the largest two are the 32nd
and 33rd according to size.
- (#??) 2^859433-1 (258716 digits); Slowinski and Gage, 1994
- (#??) 2^756839-1 (227832 digits); Slowinski and Gage, 1992
- (#31) 2^216091-1 (65050 digits); Slowinski, 1985
- (#30) 2^132049-1 (39751 digits); Slowinski, 1983
- (#29) 2^110503-1 (33265 digits); Colquitt and Welsh, 1988
- (#28) 2^86243-1 (25962 digits); Slowinski, 1983
See mersenne.txt
for more information on Mersenne primes.
- The Largest Known Factorial and Primorial Primes
- Eulcid's proof that there are
infinitely many primes used numbers
of the form n#+1. When numbers of the form n#+/-1 are prime
they are called primorial primes. Similarly
numbers of the form
n!+/-1 are called factorial primes. The current
record holders and their discoverers are:
- 3610!-1 (11277 digits); Caldwell 1993
- 1477!+1 (4042 digits); Dubner 1984
- 24029#+1 (10387 digits); Caldwell 1993
- 15877#-1 (6845 digits); Caldwell and Dubner 1992
See types.txt for descriptions of
these and other special forms of primes.
Return to table of contents.
The Complete List of the Largest Known Primes
The current list of largest known primes is available in several ways:
- all.txt
- The whole list. This is a very long list of about 10,000 primes
in a text file about 500k bytes long.
- all.zip
- The whole list (all.txt) pkZipped, so it is roughly one fourth the size of all.txt.
- short.txt
- All of the largest primes (those with 5,000 digits or more), plus the 'interesting' smaller primes (that is, those with comments on the list).
(These files are updated approximately once a month.) The following related
files are also available:
- types.txt
- Explains some of the different types of primes on the list (palindrome, Mersenne...).
- mersenne.txt
- A short note about the known Mersennes.
Finger primes@math.utm.edu for other
ways to receive these files.
Return to table of contents.
Other Sources of Large Primes
Recently there have been quite a number of excellent
books published on primes and primality proving, some of my
favorites are:
- Paulo Ribenboim, "The Book of Prime Number Records," Springer-Verlag, 1988 (QA246 .R472).
- Paulo Ribenboim, "The Little Book of Big Primes," Springer-Verlag,
1991 (QA246 .R47).
- Hans Riesel, "Prime Numbers and Computer Methods for Factorization,"
Progress in Mathematics, Birkhäuser Boston, vol. 57, 1985; and vol
126, 1994.
- D. M. Bressoud, "Factorization and Primality Testing," Undergraduate
Texts in Mathematics, Springer-Verlag, 1989.
- Henri Cohen, "A Course in Computational Algebraic Number Theory"
Springer-Verlag, Graduate texts in mathematics, vol. 138 (1993).
Also of interest is the Cunningham Project, an effort to factor
the numbers in the title of the following book.
- J. Brillhart, et al., "Factorizations of b^n±1, b = 2,3,5,6,7,10,11,12 up to high powers," American Mathematical Society, 1988.
The data from this project is
available by FTP (this site is
maintained by Paul Leyland pcl@ox.ac.uk.)
Other Web Sources:
Return to table of contents.
Notation and Definitions
- a^b, a+/-b
- Here a^b is a raised to the bth power, that is a times itself b
times (so 2^4 = 16); and a+/-b is a "plus or minus b".
- n! ("n factorial")
- If n is an integer, then n! is the product of all the
positive integers less than or equal to n, so 5!=1*2*3*4*5=120.
- n# ("n primorial")
- If n is an integer, then n# is the product of all the
primes less than or equal to n, so 6#=5#=2*3*5=30.
- Titanic Primes
- A titanic prime is a prime with at least 1,000
digits. Samuel Yates introduced this term
in 1984 ("Sinkers of the Titanic", J. Recreational Math.
17, 1984/5, p268-274) when
there were only 110 such primes known; now there are
about 10,000 known!
- Gigantic Primes
- A gigantic prime is a prime with at least 10,000
digits. This term was also introduced by Samuel Yates.
Return to table of contents.
Euclid's Proof of the Infinitude of Primes
Kummer's restatement of Euclid's proof is as follows:
Suppose that there exist only finitely many primes p1 <
p2 < ... < pr. Let
N = (p1)(p2)...(pr) > 2.
The integer N-1, being a product of primes, has a
prime divisor pi in common with N; so,
pi divides N - (N-1) =1, which is absurd!
Quoted from page 4 of Ribenboim's "Book of Prime Number Records"
mentioned above. Ribenboim's book contains
"nine and a half" proofs of this theorem!
Return to table of contents.
Comments, Suggestions? New records?
In order to help me maintain these lists please send any corrections,
comments, suggestions, flames, related WWW links and especially any
new titanic primes to
Chris Caldwell
(e-mail to: caldwell@utm.edu or
primes@utm.edu)
(Do you know about other sources of prime information? If so,
then please let me know!)
Return to table of contents.
[ Chris Caldwell |
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