If you're using them as foreign keys, then it sounds to me that you're not working with numbers, but rather with strings that happen to made entirely of digits.

In general, if you're not doing any computation, then don't use numeric values. Do everything with strings.

xoxo,
Andy

%_=split/;/,".;;n;u;e;ot;t;her;c; ".   #   Andy Lester
'Perl ;@; a;a;j;m;er;y;t;p;n;d;s;o;'.  #   http://petdance.com
"hack";print map delete$_{$_},split//,q<   andy@petdance.com   >