to get phone number programmatically in Android

With API Level greater than or equal to 22 : You can access all the SIM details using SubscritionManager. Use following command to list all Sim numbers(Works well for Dual Sim also):

List<SubscriptionInfo> list = SubscriptionManager.from(getApplicationContext()).getActiveSubscriptionInfoList();
for(SubscriptionInfo s : list){
   Log.d("SIMMANAGER",s.getNumber());
}

Note : This only works well when the operator stored their mobile number in sim card. Else, this method returns null.

I think Sim serial Number is unique. You can try this.

TelephonyManager telemamanger = (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE);
String getSimSerialNumber = telemamanger.getSimSerialNumber();

Let me know if there is any issue.

Look for TelephonyManager.getSubscriberId(), this will give the unique id for each SIM.

This is a known issue. Many SIM across the globe would return null. You should rather use IMEI number however even that can return null.

TelephonyManager.getDeviceId()