Calls, mocks my response when answering, then hangs up.

Spam. Never an answer or a message.

Constant calls. Clearly spam.

totally irritating

I've also been getting calls from this number almost every day for a few weeks now. They don't leave a message, and when I answer there is no response on the other end, they just hang up after a few seconds.

Got several calls from this number and finally spoke to someone who was fundraising for the Kennedy Center.

Same here.

This is outrageous that people can call like this.  It is harassment and intimidation.  Obama ought to do something about it.

Received call at home from this number. There was no response when I picked up and said, "Hello."
I called the number back and got a recording to the effect that "The office is closed...we are a company that provides a list of clients to charitable organizations...blah, blah, blah."
From my past experience with companies like this, it appears that they robotically call numbers to determine which are active, working telephones; those numbers are then placed on a "List" which is sold to other organizations/telemarketers so they can call your number to sell you various "Offers."
I have been on the government's "DNC" list, but apparently that means nothing.

Same here