There are far more, in fact. Each of these collaborations have around 3000 members, but there are also other experiments (LHCb, ALICE are the two big ones but there are some smaller ones too) and then there is also the team of accelerator physicists that operate the LHC.

All in all I think it is closer to 10000.

According to https://jobs.web.cern.ch/faq/all there "are over 2,250 staff members" "but there can be up to 13,000 people on site at any one time".

Those are jobs for the CERN facility alone (which also probably includes services like HR, translation, janitorial, etc). But thousands more work essentially full time as "CERN users". These scientists and engineers are typically paid by member organizations around the world, i.e. universities (think professors, postdocs, grad students) and national labs (LBNL/Brookhaven/Fermilab etc in the US, in2p3 in France, DESY in Germany).

The ATLAS and CMS author lists are about 3000 each (generally all physicists), but all told there are over 10,000 scientists, technicians, and engineers who basically work full time running the LHC and its associated detectors.

That's not to mention all the people working on any of CERN's many other projects that have nothing to do with the LHC.

"nothing to do with the LHC"

Or possibly nothing to do with physics - I went to a conference at CERN in '94 about one of their computing projects.

I believe that project became quite popular.

Yes. The ATLAS Collaboration publications have around 3,000 authors:

http://arxiv.org/find/hep-ex/1/au:+Collaboration_ATLAS/0/1/0...

Maybe it's the closest to the Manhattan project or Apollo program that Europe has had.

I respectfully disagree. 1) The Manhattan project is not comparable in scope: Both the UK and France developed nuclear weapons on their own. 2) This is not a European project per se. Most of the developed nations in the world contribute, and as such this is very much a project for and by humanity itself.