Amazon's Appstore has passed the all-important 50,000 app mark after less than 18 months. The retail giant launched the Appstore back in March last year as a precursor to the November release of its Kindle Fire tablet, luring in Android users with exclusive and free app promotions. It surpassed 30,000 apps six months ago and, according to the official store figures, now offers 50,505 Android apps.

Although we recently confirmed an Amazon smartphone is in the works, the company is widely expected to launch a pair of Kindle tablets today — so how many of those 50,505 apps are going to be compatible with the new tablets? The Appstore lists 31,429 as being Kindle Fire compatible — a very healthy figure, but many of those apps may not be optimized for tablets.