Well... I found Lingua::EN::Numbers::Ordinate in CPAN which doesn't do exactly what you want, but might help you solving your problem.

update: I just couldn't believe that there wasn't a module that did what you want, so I kept searching and just found Lingua::EN::Nums2Words which does exactly what you want.

acid06
perl -e "print pack('h*', 16369646), scalar reverse $="