factor - factor a number


        % factor [I<number ...>]


The factor utility will factor positive integers less than or equal to 2^32 - 1. When a number is factored, it is printed, followed by a ``:'', and the list of factors on a single line. Factors are listed in ascending order, and are preceded by a space. If a factor divides a value more than once, it will be printed more than once.

When factor is invoked with one or more arguments, each argument will be factored.

When factor is invoked with no arguments, factor reads numbers, one per line, from standard input, until end of file or error. Leading white-space and empty lines are ignored. Numbers may be preceded by a single - or +. Numbers are terminated by a non-digit character (such as a new-line). After a number is read, it is factored.


factor has no known bugs. This documentation corrects a bug in the BSD implementation of factor, which incorrectly states that factor will accept negative integers.

Dana Jacobson provided a fix for numbers close to perfect squares.


The Perl implementation of factor was originally written by Jonathan Feinberg, and modified by Benjamin Tilly,


This program is copyright (c) Jonathan Feinberg and Benjamin Tilly (1999).

This program is free and open software. You may use, modify, distribute, and sell this program (and any modified variants) in any way you wish, provided you do not restrict others from doing the same.