Google Play services have been installed more than 10 billion times.
The app is, in reality, a package of APIs and services that have been pre-installed on Android devices that use Google apps since 2012. As such, it is the first Android app to achieve "downloads" in the 11 digits. Platform-level features can be distributed to end users through Play services. They can also track diagnostic data from devices.
Play services achieved 5 billion installs 3 years ago almost to the day, when Android was on 2 billion actively-used devices. Today, the OS is now on more than 2.5 billion active devices.