In hybrid apps, you can use the Mobile Features widget (platform supported) and apply 'numeric' as class to the textbox containing an integer value.
For hybrid mobile apps see this widget in the appstore: https://appstore.home.mendix.com/link/app/112098/Capgemini/MobileNumericKeyPadInput
For native apps it is more a stackoverflow question: https://stackoverflow.com/questions/48798415/react-native-how-to-key-number-pad-only-without-punctuations
Regards,
Ronald