OMG!!! The guy said hi and then hung up.  What's that about?!  He must have unlimited anytime minutes judging from his activity.

Called me a miniute ago.  I'm busy I normally dont answer anything outside my area code

The callers are checking/verifying phone numbers. When you answer, they log it as a legitmate phone number. They then either start their scam calls or they sell your phone number to whoever is buying... or they do both. Either way, the best way to stop scammers and telemarketers is to STOP ANSWERING YOUR PHONE when you don't recognize the number. Anyone who has legitmate business with you and has any reason to call you will leave a message, in which they identify themselves and explain why they called, as well as leave a call-back number.

did not answer call because it is not showing caller id.

Got a call at 5:10 PM Eastern Time, I'm in Michigan.
Recorded message about a new kind of home security system, said press 1 to speak to repreentative, press 2 to be removed.