How to force Drupal search.module find "111-222" page by searching "111 222"?
Looking at the API for search, it would seem that hook_search_preprocess will allow you to alter the way keywords are extracted, something like this:

function mymodule_search_preprocess($text) {
  return preg_replace('/(\d+)-(\d+)/', '$1 $2', $text);
}


I haven't tested this code, it's purely meant as a sample. It assumes your "words" are all digits as per the question.