For at least 2 weeks I've been receiving phone calls throughout the day from this number.  No message is left on the machine.

I've gotten one of those hang-up messages, too. From my caller iD, it appears to be Clean Water Action, a non-profit group working for, as the name suggests, clean water policies.

I have been receiving the same as the poster above. Hang ups--no voicemails from this caller/number.

This number has been coming in for a couple of weeks early in the morning and late at night.  It rings then when not answered will hang up with no message.  So annoying.