Number is spoofed. I suppose you could answer it but I believe it is only to confirm that someone answers making it a live number.
Best bet, block it.

Just got a call from this number.  No ID, no message.  So what's the point?

Received call. No message left. Yeah, number looks funny, with digits in sequence. I've blocked it now.

These guys are so called "process servers" for a debt collection agency trying to collect on out of SOL debt or even wrong debt.  They will try to make it sound like they work for the county, and make veiled threats like "Is Jane Doe home?  We need to know if she will be home because we have a process server and a Sheriff's Deputy (There might now even be a Sheriff's Deputy in your city) on they way to serve you papers, and Jane Doe needs to sign them."  

First of all if you have a means to record them, please do, because they are borderline breaking so many federal and state laws, you just make sure you get their permission to record the conversation as California is a two way notify state.  If you try to tell them they are wrong, they will refer you to RN or RM Associates.  Again they try to use bogus titles to scare you into thinking you will be sued, like the guy I was connected to had the title of "Litigator" and I asked if he was a licensed attorney and of course he said he wasn't !  Ridiculous! LOL.  

Just block these bottom of the pond scum feeders from your phone, or talk to them and relieve some stress.  I always have fun with these guys, because they definitely do not know what your rights are.

Thanks Kyle for the insight! I've been getting calls from this number at least twice a day. It's from my area code so I keep thinking it's a call from a friend or a relative of mine but no messages are ever left.