Who called from 6613909960

my cell phone rang once with the caller ID 661-390-9960...they hung up.  This has happened now three times over the last couple of weeks.
ITs a reward redemption site!  I have NOT gone to any reward sites, so do not call these idiots back! And the only reason I know is I used my work number to call back that number!

Picked up because it looked like a client's number (Bakersfield/Kern County, CA area code) but it was just dead air. Such a waste.

Received a call from this number today.  Didn't take the call, as I don't answer numbers I don't recognize.  Thanks, Jodie for letter us know what type of caller this is.

Rec'd a call from this number and didn't answer. My phone detected it's a California number, ..which is now on my reject list.

Got one ring from this number and they hung up. At 11:10 pm... Who is doing this and more importantly, why???