but Math::Pari has very fast factorization algorithms.

Indeed it does--blindly fast. And that completely changes the perspective on using the factors in some sort of solution. I'm still finding my way around the huge set of functions in Math::Pari. If POD allowed tables, the looong list of functions could be made more compact and easier to navigate. Even so, I doubt I would have picked out sigma as being useful in this context from the description: 

sigma(x,{k = 1})

sum of the k^{th} powers of the positive divisors 
of |x|. x must be of type integer.

The library syntax is sumdiv(x) ( = sigma(x)) 
or gsumdivk(x,k) ( = sigma(x,k)), 
where k is a C long integer.

[download]

Mmm'kay! :)

Do you have the time/inclination to post code for your solution?

Examine what is said, not who speaks.
Silence betokens consent.
Love the truth but pardon error.

In reply to Re^9: OT: Finding Factor Closest To Square Root by BrowserUk
in thread OT: Finding Factor Closest To Square Root by QM

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.