The IMSI is a fixed 15-digit length. It consists of a 3-digit Mobile Country Code (MCC), a 2-digit Mobile Network Code (MNC), and a 10-digit Mobile Station Identification Number (MSIN). Telcordia Technologies is responsible for the assignment and administration of the first six digits (the MCC + MNC) to network operators, and the network operator to which these digits are assigned is responsible for the assignment and administration of the last 10 digits (the MSIN).
