Is it compulsory to have registered mobile number to use mAadhaar services?

No. Anyone with a smartphone can install and use mAadhaar App.
Without a registered mobile number, Aadhaar number holder will be able to avail only few services such as Order Aadhaar PVC card, Locate Enrolment Center, Verify Aadhaar, Scanning QR code etc.
However registered mobile number is mandatory to create the profile in mAadhaar and use the same as digital identity and avail all other Aadhaar services. The OTP will be sent only to registered mobile for creating the profile in mAadhaar.