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GNU Info (sh-utils.info)factor invocation`factor': Print prime factors ============================= `factor' prints prime factors. Synopses: factor [NUMBER]... factor OPTION 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'. Note: 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 automatically generated by info2www version 1.2.2.9 |