International Mobile Subscriber Identity (IMSI)

The International Mobile Subscriber Identity (IMSI) is a uniqueidentity allocated to each subscriber which facilitates correct subscriber identification over the radio path and through the network. It is used for all signaling in the PLMN. All network related subscriber information is connected to an IMSI. The IMSI is stored in the SIM, the HLR and in the serving VLR.

the IMSI has a maximum length of 15 digits.

The IMSI consists of three different parts:

1st 2 digits: MCC (Mobile country code)

2nd 2-3 digits:  MNC(Mobile network code)

The rest of digits are: MSIN(Mobile station identification number)

The IMSI has a maximum length of 15 digits which consists of three different parts. Good point.