The most simplest way to check your MTN number is to dial the short code *156# then choose option 1 “Check my number“. Your number will popup after choosing this option.
You can secondly check your number using MyMTNapp. Just download and install the app from Google Play store if you are an android user or Apple store if you are an iphone user. Run the app, enter your phone number for authentication and logging in. Your name used during sim registration and phone number is displayed in the header of the app.