The following code is deprecated.
String myIMSI = android.os.SystemProperties.get(android.telephony.TelephonyProperties.PROPERTY_IMSI);
// within my emulator it returns: 310995000000000
String myIMEI = android.os.SystemProperties.get(android.telephony.TelephonyProperties.PROPERTY_IMEI);
// within my emulator it returns: 000000000000000
In order to get IMSI and IMEI, the following code works, assuming you write the code in a Activity class.
TelephonyManager mTelephonyMgr = (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE);
String imsi = mTelephonyMgr.getSubscriberId();
String imei = mTelephonyMgr.getDeviceId();
Do not forget to set <uses-permission android:name="android.permission.READ_PHONE_STATE"/> in AndroidManifest.xml.