IMEI (International Mobile Station Equipment Identity) number identifies legitimate devices using the GSM network. This 15 digit (14 digits plus a check digit in the last) number is a prominent measure to trim down the instances of using a stolen/lost mobile phone. You can locate the IMEI number of your cell phone either on the box, or printed inside the battery compartment. The IMEI number can be used by the owner of the mobile device to blacklist the phone. For this, the owner should call the network service provider and instruct them to stop any further services of the phone.
IMEI number is strictly related to the mobile device and has no relation with the user. The Telecom authorities of many countries have introduced stringent measures to make it mandatory for the manufacturers to produce devices bearing a valid IMEI number. Though law-breakers have originated many ways to change the IMEI number, they rarely opt for this due to rigorous regulatory compliances.
The digits comprising the IMEI number represent the origin, model, and the serial number of the mobile device. The initial eight digits define the model and origin, and are collectively termed as Type Allocation Code. The following six digits define the manufacturer and the last digit (check digit) is calculated using Luhn algorithm. The check digit is the function of the digits prior to it.