[Hands0n]

A handy little web utility is here http://mnnc.net/index.php

Interesting to play with if you're wondering which network someone is on.

Do please share if you've any others that you know of.

[Ronin47]

nice find thanks

[gorilla]

I'm not sure how accurate this is. It tells you on which network the number originated on i.e. if the number has been ported to another network the information provided may be incorrect. I will give the site merit though, as there are loads of people who never port and those who are on lower end contracts or PAYG will find it useful to know who is on the same network as them.

[Ben]

Indeed, it's useful for looking up what network was originally assigned a given number, rather than what network a number currently resides on. The former is information provided by the regulator, where as the latter usually involves a small charge.

It's nice to see the site has taken the information and made it more accessible.

Commercial solutions (http://www.cardboardfish.com/products/aggregatoroperator/hlr_lookup.html) exist for this sort of thing, often used by organisations that hold a lot of mobile numbers so they can clean up their data.