Happy 4sqDay. Since (for those of us who remember math class from school) four squared is 16, Foursquare has made a habit to celebrate on April 16.

To mark the occasion this year, CEO Dennis Crowley decided to celebrate with a video. Click here if you can’t see the video.

And Crowley took the time to announce some interesting statistics regarding the check-in app. On Foursquare, there are more than 35 million places, 2 billion overall check-ins and 20 million users. He didn’t quantify if the 20 million number is active users or simply the number of times the app was downloaded. But it’s still an impressive number.

Users who check in sometime today using the service will also receive the nifty, pictured 4sqDay 2012 badge.

Foursquare is available in the App Store for free.

Do you still use Foursquare? While other, competing startups like Instagram have made waves in the technology world, does the check-in giant have what it takes to succeed in the long term?

(Via The Verge)