Got a call today PST 9:30 AM from this number. I have been getting lots of unknown calls similar to its character.
My theory is that once you even answer an unknown number a machine records this as "IS" a good number than that information gets passed on as a list of good numbers and is available for sale to illegal telemarketers. My advice is to put a distinctive ring on all of your known contacts in your cell phone book and make a permanent habit of looking at the phone before you answer anyone ringing the cell phone's "default" ring tone. If the call is important they will leave voice mail so you could call right back.
I am afraid that the above procedure is our only line of defense as the Government Do Not Call List just does not do well with cell phone numbers.