Java Glossary : primes

Java definitions: 0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

You are here : home : Java Glossary : P words : primes.

primes

A number divisible only by itself and one. Primes are useful in constructing Hashtables. You can download Java source code to perform an Eratosthenes sieve to compute the primes, whether a number is prime, or the next prime above or below a given number. Mitch Gallant has posted some methods to test if an individual number is prime. Try BigInteger.isProbablePrime for determining if huge numbers are prime.

Mersenne primes are convenient for computing. The have the form 2ⁿ-1. The Mersenne primes that fall into the range of longs are:

Mersenne Primes
n	2	3	5	7	13	17	19	31	61
2ⁿ-1 (hex)	0x3	0x7	0x1f	0x7f	0x1fff	0x1ffff	0x7ffff	0x7fffffff	-0x1fffffffffffffffL
2ⁿ-1 (decimal)	3	7	31	127	8,191	131,071	524,287	2,147,483,647	2,305,843,009,213,693,951

The largest Mersenne prime found as of 2002 May 24 was 2^213466917-1.

See BigInteger.isProbablyPrime().

factoring ¤ Hashtables

home	Canadian Mind Products
	mindprod.com IP:[24.87.56.253]
	Your IP:[80.134.30.163]
	You are visitor number 978.
	Please send errors, omissions and suggestions
	to improve this page to Roedy Green.
	You can get a fresh copy of this page from:	or possibly from your local J: drive mirror:
	http://mindprod.com/jgloss/primes.html	J:\mindprod\jgloss\primes.html