I'm sorry I was wrong in my previous post, looking at the source I've found it's not true
Hibernate Search automatically pads "0" to numbers.
I should add that even if you indexed all numbers correctly a RangeQuery could be dangerous, especially if you have many possible different values,
look for "Why am I getting a TooManyClauses exception?"
in the Lucene FAQ:
http://wiki.apache.org/lucene-java/LuceneFAQ
If you are aware of the dangers of a RangeQuery but still want to use it you should implement your own StringBridge, and use org.apache.lucene.document.NumberTools.