On Google’s earnings call today, Jeff Huber, Senior VP Commerce and Local, revealed that there have been over 3 billion Android apps installed. And downloads of Android apps are up 50 percent from Q4 2010.

Huber also mentioned that 350,000 Android devices are being activated per day, a data point which was revealed this past week. In terms of breaking out share by device and market, Huber said the company doesn’t reveal these numbers. But he did say that with device partners, there is strength in U.S., Japan, Korea, and Europe specifically. He added that international is growing as a whole in terms of Android usage.

To put the 3 billion stat in perspective, Apple just passed 10 billion app downloads in January. But thanks to the fast growth of the sale of Android phones, Google’s app downloads are growing fast. The first billion installs took 20 months, the second billion installs took another 5 months, and the third billion took only 2 months. I’m guessing the 4 billion mark will take less than

It’s also important to note that because of Google’s open platform, Android users can download apps from a number of marketplaces, including Google’s Android Market. Amazon just launched an Android App Store a few weeks ago.

What’s also unclear how many of these apps installed were free compared to paid apps. We’ve heard in the past that more Android apps are free compared to Apple’s apps.

In the Q&A portion of the call, Huber said there are many exciting products and innovation coming along to the Android platform, but didn’t reveal any specifics. In the call, CFO Patrick Pichette commented that the Android platform is growing “amazingly blazing” and that Google stumbled into a billion dollar business with respect to Android and mobile.