How many Publishers does 

AUTODESK App Store have?

Though a "Show all" button is not provided in Publishers tab, a simple search with blank parameter still return a reasonable result:

988 

publishers available on AUTODESK App Store. 

That means, on the average, each publisher owns 3.8 Apps.  However, the result seems not up-to-date, or the App number of each publisher is not up-to-date.  Also, there are many publishers I haven't ever seen on the Apps page.