I strongly recommend installing Math::Pari. The following short script will give you a picture of what state of the art factoring algorithms do:

#! /usr/bin/perl
use Math::Pari qw(:int factorint);
print factorint($_), "\n" for @ARGV;
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Sample output:

bash-2.01$ ./factor 491320487930121938479123 4839013210437894323
[48049,1;10225405064207828227,1]
[11,2;36809477,1;1086455119,1]
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With barely a pause, even on this creaky old laptop.

It does have to think, though, about:

bash-2.01$ ./factor 4913204879301219384791234839013210437894323
[3,1;19,1;82471,1;17992995173,1;4100172797059,1;14167170962387,1]
[download]