I looked at some statistics last time in 2011, almost a 4 years back. Interesting to observe the changes and the evolution.
You can find the facts at AppBrain (http://www.appbrain.com/stats)
From ~175.000 applications in 2011 the number passed 1,5 million in February 2015. Surprisingly the number of apps with in-app billing is only 108.000. It feels like almost any application comes with this “feature”, pretty much every serious game.
I also logged into the developers console again, just remembered I published some simple apps in 2011 to learn about the physics of the appstore.
Interesting enough they were downloaded 700+ and 200+ times. Wonder what figures this experiment would render when I start it again.
I also checked the current number of Hello World apps (usually the first app any developer ever create in any new programming language or tool). 900+ apps with the keywords “hello world”.
One of them installed 10.000+ times. Amazing for an app that does nothing.
Also other test apps that do nothing.