MSISDN is a number uniquely identifying a subscription in a GSM
or UMTS mobile network. Simply put, it is the telephone number to
the SIM card in a mobile/cellular phone. The abbreviation has
several interpretations, most common one being "Mobile Subscriber
Integrated Services Digital Network Number".[1] The MSISDN together
with IMSI are two important numbers used to identify a mobile
phone. IMSI is often used as a key in the HLR ("subscriber
database") and MSISDN is the number normally dialed to connect a
call to the mobile phone. The MSISDN follows the numbering plan
defined in the ITU-T recommendation E.164. More Details in
http://en.wikipedia.org/wiki/MSISDN