This is a spoofed (faked) telephone number. Moreover, it is in an INVALID format. Consequently, you should expect (if you answer the call) to be speaking with a scam artist or listening to a robo call (pre-recorded message), which incidentally is illegal.
North American phone numbers are in the format: NXX-NXX-XXXX where N is any digit from 2-9 and X can be any digit from 0-9. Check out the rules at the North American Numbering Plan Administration website: http://www.nanpa.com/
If you receive a call from this faked out number, or any other number that does not conform to the NANPA rules, I suggest you report the call immediately to the "Do Not Call" list regulator for your country. You can also initiate a call trace by dialing *57 (or #57 in some areas; there might be an altogether code in other areas - check the front of your phone directory). Anyway, the phone company will trace the call and be able to produce the records (for the police) if you decide to take legal action; they will not release the records to you directly.
I have received a dozen calls with "406" on the caller id in the past 24 hours. I actually answered a few times to get only silence BUT one time a guy claiming to be from a "sweepstakes" was on the line - there was a ton of background noise - he asked if I carried a Visa or MasterCard, when I said no he hung up. Yet the calls continue...I am in the 941 area code.
For tha past 2 days I have been receiving calls from 3 to four digit numbers but unfortunately missed every one of them but there was no message left on my cell phone. The first number that called was 271-6, the 2nd was 624, the third was 252-8, and the fourth showed up as 402. It's driving me crazy wondering who the hell could be calling me with a 3 or 4 digit number since I've never seen this before. Does anyone have any idea who could this be and have these numbers evershowed up on your caller id???