Mobile station international subscriber directory number definition
Mobile station international subscriber directory number (MSISDN) refers to the number that is uniquely associated with every SIM card in GSM and UMTS networks. It is the full phone number, including country code and area code, of the mobile station (the phone or device). For example, +1 is the country code, 212 is the national destination code, while 555-1234 is the subscriber number. All of these numbers together make up the mobile station international subscriber directory number.
See also: mobile network operator
MSISDN vs IMSI
Sometimes, MSISDN can be mixed up with IMSI, or international mobile subscriber identity number. MSISDN is the number used for routing calls and SMS to the right phone. In other words, it’s your phone number you would give other people. IMSI, on the other hand, is the unique code stored in your SIM card. It is used to authenticate and connect a device to the mobile network.
Unlike MSISDN, IMSI is not a public number. It’s used for technical and security reasons, but you rarely have to share it. IMSI also doesn’t change. Even if you changed your phone number but kept your SIM, your IMSI number would stay the same, while your MSISDN would be different.