A Brief Guide to HLR Lookups

"HLR Lookups make it possible to check the status of any GSM cell phone number. By making a query to the Home Location Register, the lookup service determines whether that number is valid, whether it is currently active in a mobile network, and if so which network, whether it was ported from another network, and whether it is roaming. The query will also return meta information such as the IMSI, MSC, MCC and MNC." - A Brief Guide To HLR Lookups (PDF), November 2014

How HLR Lookups Benefit Businesses and Organizations

"With the development of Mobile Number Portability, cell phone subscribers can now keep their number if they change mobile networks. This is great news for phone users but costly for businesses, market research companies, insurance agencies, travel agencies, universities, and other organizations that periodically call or send text messages to large numbers of people in their database. One reason: Many of those phone numbers frequently may no longer be active.
HLR Lookup is a service that gets around this. There are several ways an HLR Lookup service can save you time and money—and in a competitive market, this advantage can be critical. This paper describes a few of those ways." - How HLR Lookups Benefit Businesses and Organizations (PDF), November 2014