My guess this is either a bill collector or a server. He is tring to see if you are home, if they are not saying anything. I have many unpaid bills, and I only get this type of calls on a specific phone number from bill collectors. The white pages indicates that it is a land line.

Anyone who has 666 in their phone number must be evil.

Calling at inappropiate times, Sundays, no message and dosen't answer when called back.....

Calls at 8am and no is there if I pick up to chew them out.
Never leaves a message.
How do I block this number?

I get calls from this number on a regular basis, and it appears to be local to me but I don't know.  I just ignore it.  If someone doesn't want to get a hold of me bad enough to leave a message, then they don't need to talk to me.  If they want to waste their time, so be it.

spoofed phone number from bottom feeder collection agency called BCS