Apparently September 17th is Constitution Day. This is the day in 1787 when the document was signed. (July 4th is for the Declaration of Independence.) Schools receiving Federal funding are supposed to spend part of the day teaching about the Constitution.

I wonder how many people have a copy of it?

If you have an eBook reader, then you should be able to get a free copy of the United States Constitution. Because it is in the public domain, anyone can publish it for free. Project Gutenberg posted it back in 2003.