Overview#International Mobile Subscriber Identity (IMSI) is a Unique Identifier on all Mobile Networks of the End-User by the Mobile Network Operator (MNO) and is stored as a 64 bit field and is sent by the phone to the network
International Mobile Subscriber Identity is used in any Mobile Network that has an Interconnection with other networks. For GSM, UMTS and LTE networks, this number was provisioned in the SIM card and for cdmaOne and CDMA2000 networks, in the phone directly or in the R-UIM card (the CDMA equivalent of the SIM card). Both cards have been superseded by the UICC.
The format is:
- The first three digits represent the Mobile Country Code (MCC).
- The next two or three digits represent the Mobile Network Code (MNC) although three-digit MNC codes are allowed by E.212 but are mainly used in the United States and Canada.
- The next digits represent the Mobile Subscriber Identification Number (MSIN).