My husband has Google Voice number on his phone he states he doesn't know where it come from the states he doesn't have a Hangout app but I find history where he's been on there.../QUOTE]
A Google Voice phone number is its own, valid phone number, so he doesn't have to use just the Hangouts app to use it (and just as an aside last year Google announced it will be splitting up the Hangouts app as a focal point for several different services into their own separate ones). The Google Voice app and a number of text messaging apps will work with a GV number too. It's also tied directly to his online Google account so if you also have access to that, once he had applied for and received his GV number, it will be an integral service in his Google account, just like Gmail, Google Calendar, Google Drive, etc.
Try going to:
https://voice.google.com
and log in using his credentials.
https://en.wikipedia.org/wiki/Google_Voice