A general dictionary would define primality as “the quality or condition of being a prime numberMathworldPlanetmath.” In mathematics, it might be more useful to define primality as a Boolean-valued function that returns True if the input number is prime and False otherwise. Two examples: the primality of 47 is True; the primality of 42 is False.

It is not necessary to perform integer factorization to know the primality of a given integer, as there are various congruencesMathworldPlanetmathPlanetmathPlanetmath and other relationsMathworldPlanetmath which prime numbers satisfy but non-primes don’t; these can serve as primality tests. The primality of certain large numbers, such as the thirtieth Fermat number, has been determined even though all we know of its least prime factorMathworldPlanetmath is that it is less than the square root of the composite Fermat number. Before the primality of a large number is ascertained, it might be considered a probable primeMathworldPlanetmath. 1 is the only integer to be declared non-prime without a previously unknown factor being discovered.

Title primality
Canonical name Primality
Date of creation 2013-03-22 17:45:33
Last modified on 2013-03-22 17:45:33
Owner PrimeFan (13766)
Last modified by PrimeFan (13766)
Numerical id 6
Author PrimeFan (13766)
Entry type Definition
Classification msc 11A41