IMEI (International Mobile Equipment Identity) is a unique 15 (or 16 digit for IMEISV) number assigned to all cellular devices which identifies your device within mobile network. IMEI number only identifies device and not the subscriber.
IMEI number depends on device capability for handling sim cards. If a phone has single sim then there will be a single IMEI number for the device.
However, if device is dual sim capable then it will have two IMEI numbers for the same device. Device with 3 sim capability will have 3 IMEI numbers, while device with no sim capability like some models of Android or Apple Tablets will have no IMEI numbers.
IMEI number of a device can be found in following ways:
1) In most of mobile phones the IMEI number appears on display when user enters *#06# (star pound zero six pound) in keypad and press call or send.
2) IMEI number can also be found printed inside battery compartment of phones with removable battery.
3) It can be found on device bill or package.
IMEI (International Mobile Equipment Identity) is like the registration number of your vehicle.
1) IMEI is part of the GSM and 3GPP standards for mobile devices
2) IMEI numbers are being allotted by four bodies authorized by GSMA.
3) From IMEI number one can identify the make and model of the handset.
4) No two mobile handsets in the world should have the same IMEI number.
5) IMEI number is an important tool for the handset tracking.
Structure of IMEI Number:
|TAC - Type Allocation Code||Serial Number||Check Digit|
|Reporting Body Identifier, e.g. MSAI||Type Identifier defined by MSAI||Number range allocated by MSAI but assigned to individual mobile stations by the manufacturer.||Defined as a function of all other digits (calculated by the manufacturer).|
How it works?
Every time a phone uses a network to make/receive a call or send/receive a message, its IMEI number is emitted and tracked. Service providers have databases in which these numbers are stored and categorized in white or black lists.
An owner can report his/her mobile device stolen and it can be tracked using IMEI number if that device is active on network. They can also make it blacklisted after theft.
Although it is difficult to change IMEI number because it is embedded on handset, however, some people may be able to change it with professional tools. Once IMEI number of a device is changed then it is taken as a completely different device by network.