I don't know the exact numbers, but when I left Microsoft a couple of years ago, the following product divisions were among those based in the 6 buildings of the Mountain View SVC (https://www.google.com/maps/place/Microsoft+SVC+Building+1/@... ):

- Outlook.com (formerly Hotmail)

- Parts of Office for Mac OS X and iOS

- Xbox hardware and accessories (Xbox software was in Redmond)

- Windows Phone online services

- Microsoft Research Silicon Valley (but that was closed in the first round of layoffs several months after I left)

SVC was originally built for Hotmail and WebTV (remember that?).

Microsoft also had separate offices in Sunnyvale (in the big cluster of relative skyscrapers just south of Moffett Field), which I believe were mostly folks who came from Skype and/or Nokia.