So, if you have a GSM handset, it comes with an IMEI number It is a unique 15-digit number that identifies your gadget. It is interesting that phones that have no SIM card slot also have no IMEI number. And CDMA gadgets have a different identifier, MEID code. We can compare the IMEI to a human fingerprint. There are no two devices with the same 15-digit code, just like no two people with the same fingerprints.