USSD code means Unstructured Supplementary Service Data. Across the country, these codes are available to mobile phone users on prepaid plans. Additionally, these codes prevent people from having to contact customer care for every small issue. To check the Airtel mobile number via USSD code, you can follow these steps:
1. Open the phone and Dial *282#
2. You will get a message on your phone screen with your Airtel mobile number that looks like, “Hi, Your Mobile no. is: xxxxxxxxxx”
3. Note it down on paper or notepad

For more read - https://onlinegeeks.net/how-to-check-your-airtel-number/