How can I index/search Numbers in Lucene?

Made up an Lucene Index, added the needed fields to it, and tried to search for the entries. Everthing works fine as long as i don't search for numbers (etc.: "1234")(which i need to do)

I added the fields with numbers in it as keywords, so that no tokenizing happens, but still i get no results. (I use a Simpleanalyzer for the normal text fields)

Is there something special to consider when working with numbers, or could it be that i'm simple doing something wrong? But since it works fine with normal text i think numbers need a special treatment ...