In my limited testing Math::BigInt is two orders of magnitude faster than the next module I tried. At least it was on my crummy ole laptop. Just make sure to install the multicore module Math::BigInt::GMP as well which it uses to good advantage.

# Runtime:  0.15s user 0.02s system 41% cpu 0.418 total
use Math::BigInt lib => 'GMP';
my $b = Math::BigInt->new(35000);
print $b->bfac(),"\n";
[download]