All mobile devices are identified by an electronic serial number (ESN) or a mobile equipment identifier (MEID) or a international mobile equipment identity (IMEI).
An ESN is an 11-digit number. An ESN in hexadecimal, or hex, is represented by eight characters that are numbers and letters. The first digit is always one of A-F.
Example of ESN: 12345678901
Example of hex ESN: A0123456
An MEID is always hexadecimal, represented by 14 characters that are numbers and letters. The first digit is always one of A-F.
An IMEI is always numeric. IMEI is represented by a minimum of 14-digits and a maximum of 16-digits.