A IMEI number or the International Mobile Equipment Identity, is a unique set of numbers, usually 15 numbers, that is used to identify a cellular device. Every device that connects to a cellular network needs to have a unique IMEI number. Unlike SIM cards, which are linked to the cellular account or phone plan, IMEI numbers are directly linked to the device itself, remaining the same even if phone plans or cellular networks change. IMEI numbers are assigned and generated by the GSMA.
IMEI numbers have 15 numbers, consisting of 14 unique identifing numbers with the fifteenth number being a checksum. The first two digits are the reporting body identifier. It is followed by six numbers that identify the manufacturer and the phone model. Then those numbers are followed by another six numbers for the devices’ serial number and it is ended with a checksum.