Hi Bri,
I'm not actually sure about the true number (or is there a way to find out unless it's been discussed in an article somewhere), but I imagine it's in the hundreds. Each app (Word, Excel, PowerPoint), is a product in its own right so I figure maybe
a hundred devs worked on that. Don't forget there are also testers, SDETs (developers who write automated test cases), and program managers. I'm sure that we're talking about maybe 1000-2000+ people easy for the whole office suite.
-Erwin, Microsoft Learning