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`factor`

: Print prime factors
`factor`

prints prime factors. Synopses:

factor [ |

If no `number` is specified on the command line, `factor`

reads
numbers from standard input, delimited by newlines, tabs, or spaces.

The only options are ``--help`' and ``--version`'. See section 2. Common options.

The algorithm it uses is not very sophisticated, so for some inputs
`factor`

runs for a long time. The hardest numbers to factor are
the products of large primes. Factoring the product of the two largest 32-bit
prime numbers takes over 10 minutes of CPU time on a 400MHz Pentium II.

$ p=`echo '4294967279 * 4294967291'|bc` $ factor $p 18446743979220271189: 4294967279 4294967291 |

In contrast, `factor`

factors the largest 64-bit number in just
over a tenth of a second:

$ factor `echo '2^64-1'|bc` 18446744073709551615: 3 5 17 257 641 65537 6700417 |

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