Less than a week following the release of Instagram for the Android platform, the popular photo-sharing app has already hit the 5-million download mark as shown in Google Play Store’s stat.

That’s a remarkable feat for an Android app, noting that its iOS counterpart took about half a year to reach 5 million users. Instagram for Android was also seen downloaded 1 million times in less than a day following its official launch to Google Play Store.

On a side note, Facebook announced on Tuesday that it acquires Instagram for a whopping $1 Billion in cash and stock. That’s huge money for a startup that still has to celebrate its 2nd anniversary comes October and doesn’t even make any revenue just yet. But for Facebook, the move is smart enough to keep its dominance for the best social photo sharing experience. And now you’d incline to believe that if “video” is for Google (through YouTube), then “photo” is for Facebook (through the social network itself and Instagram).

Instagram’s acquisition however, has nothing to do with the first 5-million download milestone in Android platform – but possibly the numbers could ramp up in the future, thanks to Facebook’s gigantic user base. [via]