No-no-no, that would be too trivial.
Before posting I trying to search using attribute uidNumber,
attributetype ( 184.108.40.206.220.127.116.11 NAME 'uidNumber'
DESC 'An integer uniquely identifying a user in an administrati
SYNTAX 18.104.22.168.4.1.1422.214.171.124.27 SINGLE-VALUE )
with the filter 'uidNumber <= 1000' and still got no answers. Your supposition may be correct, but it does not answer the second question - how can I do a search with given filter, treating numbers as numbers?