Bizarre decimal number to in-addr-arpa mapping......

[Michael Fenton]

I discovered that people on my network are getting around
our web filtering by using decimal number URL's.
Check this out:
gunk:~$ nslookup 3489040081
Server:  server.tt.net
Address:  209.98.124.2

Name:    teen-space.com
Address:  207.246.134.209

How the hell does 3489040081 resolve?
I did a little looking and it seems to map somehow
to an inaddr-arpa address......

Anybody know what's going on here?

Thanks,
Michael Fenton