IMEI is the unique number that identifies your phone/gadget.

It can mostly be found on a white label at the back of the battery slot. It should be 15 or 17 digits long, not including a few forward slashes, and shouldn't contain any letters.

Only the first 15 digits are needed. On an iPhone, the IMEI number can be found on the SIM tray. The IMEI number is also printed on the box of every phone.

Alternatively, you can always find your IMEI by typing in *#06# and the number will be displayed on your phone.