Different results for my low cost chinese tablet. It's not a phone so why getDeviceId() returns a number that seems to be a valid IMEI?
C:\>adb shell dumpsys iphonesubinfo
Phone Subscriber Info:
Phone Type = GSM
Device ID = null
but using
TelephonyManager tManager = (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE);
String uid = tManager.getDeviceId();
uid = 35881700... (I'm not showing the whole IMEI number for privacy)