The simple & easiest way would be to call up the number & check it up. But obviously we can’t do that if there is bulk data to check. In such cases, I recommend you using our phone number validation tool. We provide 100 Free credits while you sign up. The validation of data can be either instant or bulk verification. We also provide an option to integrate & make API setup with your website. This filters out entry of any invalid contacts in your database. Along with ascertaining the validity of the number, this platform also helps you with information like carrier type, Mobile type, Geolocate , timezone,Formatting etc.To auto verify,the best option will be to use real-time Phone validation API to easily integrate into website forms or mobile apps and make sure only valid numbers are accepted to your contact list and improve overall user experience at the time of capture.