In Android, there exist two different 'Android IDs'. This is a simple App to display the unique ID of any device.
A 64-bit number (as a 16 digit hex string) that is randomly generated on the device's first boot and should remain constant for the lifetime of the device. (The value may change if a factory reset is performed on the device.)
A 64-bit number (as a 16 digit hex string) that is randomly generated on the device's first GSF login and should remain constant for the lifetime of the device. (The value will change if a factory reset is performed on the device.)