Something about the number looked scammy, especially the 666 prefix, but halfway through my outgoing message I did pick up, and all I heard was dead silence.  I didn't say hello a second time, I just hung up.  These scam callers run in topical groups.  Lately, it's been scam mediocre brace sales, and now scam cold-calls asking if you are a drug addict who needs to be referred for treatment.  I would guess they're the latter but cannot prove it unless they try again, and then it will be obvious.  I won't answer next time, though.

I called the number back and it was reported as an 'non-working' number---strange, they could call me, but I could not call them.