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;

[download]
Sample output: 
bash-2.01$ ./factor 491320487930121938479123 4839013210437894323
[48049,1;10225405064207828227,1]
[11,2;36809477,1;1086455119,1]

[download]
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]

In reply to Re (tilly) 1: Factoring Decimal Digits by tilly
in thread Factoring Decimal Digits by Yossi

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.