Gengar Studios, the developer behind the simple and free Brain Tuner [Free, App Store] application, was kind enough to pass along the download stats for what was the #2 App Store App last week. Brain Tuner is a simple brain exercising app in which you mark simple math equations as right or wrong.
The app shot up in popularity soon after its release and peaked as the 2nd most downloaded application for a couple of days. Even now, it sits in the #4 spot.
Based on the given data, it appears the number two spot on the App Store generates over 60,000 downloads a day.
If you look in the App Store, you'll find the application was originally published under developer Bridger Maxwell who is responsible the iPhone game Lumen [App Store]. Gengar Studios will be branching off under their own name and has also passed along that they are available for iPhone programming.