I couldn't find a number for how many iOS users there are, but the latest numbers show 316 million iOS devices have been sold, so that means per each iOS device, about 77 applications have been downloaded. That's much higher than I would have expected.
I know people like big numbers, but I'm not sure how significant the number of apps is given that many of them are less app and more replication of a Web page, or serve to make a Web page's content more usable on a handheld device.
My iPhone tells me i have purchased 463 iphone apps since 2009 (2 devices)