Receive calls from this number about 5 times a week.  When I answer a computerized voice says "sorry...that is not a valid answer" and it hangs up.

This number, and a string of other 940 and 817 numbers, has called our business 800 numbers multiple times.  No fax (though, sounds like a fax tone), no one on the phone, no way to look them up or ask them to stop calling.  Filing a Junk Fax 1088 Form with the FCC, recommend you do so as well, or you can fill out a Do Not Call Complaint with the FTC if you're not a business.  The more people who report this, the louder we are, the faster we get the FCC's attention, the more likely they do something about it.

FCC:        
https://esupport.fcc.gov/form1088/consumer.do?form_page=1088A

FTC:
https://www.donotcall.gov/complaint/complaintcheck.aspx

Clogging up my 800 number with an automated fax.

This is one of very many automated fax calls originating from Texas. My home, business and cell phones ring at the same time.