NAME

factor — factor a number

SYNOPSIS

factor

[number ...]

DESCRIPTION

The factor utility factors integers larger than 1. When a number is factored, it is printed, followed by a “:”, and the list of (prime) 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 +. Integer less than 2 are rejected. Numbers are terminated by a non-digit character (such as a newline). After a number is read, it is factored. Input lines must not be longer than LINE_MAX - 1 (currently 2047) characters.

By default, factor is compiled against the OpenSSL bignum implementation openssl_bn(3), which lets it handle arbitrarily large values. (Note however that very large values can take a very long time to factor.) If factor is compiled without OpenSSL it is limited to the maximum value of unsigned long.

DIAGNOSTICS

Out of range or invalid input results in an appropriate error message being written to standard error.