Microsoft’s Windows Phone Marketplace has now reached 20,000 applications.

The software giant only recently announced that it had 18,000 applications, during a VIP Windows Phone Mango event earlier this week. Microsoft has approved over 1,200 apps just this week, further evidence of the Marketplace growth rate. Microsoft’s Windows Phone 7 Marketplace has taken 219 days to reach 20,000 apps since launch. Apple’s iPhone App Store took 215 days and Google’s Android store took 419 days. The speed of application growth shows that Microsoft is doing well with its app momentum.

Marketplace trackers windowsphoneapplist.com is currently tracking 19,789 apps in the U.S. Marketplace alone. WP7applist is tracking 20,185 applications worldwide and explains 1,166 of them are inactive, 48% are available for free and the average price is $1.45 per paid application. Microsoft’s Windows Phone Marketplace is growing at an impressive rate. The software giant added 3,000 applications in April alone after reaching its 12,000 milestone in late March. The Marketplace passed 15,000 apps in April just in time for its six month birthday. WP7applist says that 175 apps are updated on average each day. In the last 24 hours, 99 apps were updated and 288 were added.

Windows Phone 7 launched on October 26 with 1,000 applications available. Six months later and the platform has increased impressively. Microsoft appears to be building up a good momentum amongst application developers. Microsoft says it now has over 32,000 Windows Phone application developers, who deliver an average of 100 new apps per day. The Windows Phone Developer Tools have now been downloaded more than one million times.

Despite delays with its first platform update, “NoDo”, developers have a lot to look forward to this year. Microsoft’s new Nokia partnership is a great opportunity for new and existing developers as more and more consumers take advantage of Windows Phone. Nokia said recently that it plans to ship Windows Phone branded devices to developers when they are available later this year. Nokia is currently engineering Windows Phone devices and is expected to wait for “Mango”, the next version of Windows Phone, until it unveils them later this year. “Mango”, the codename for what will likely be named Windows Phone 7.5, is currently in the final development stages at Microsoft. The software giant revealed a number of new enhancements recently and promised over 500 features at launch. Nokia has also promised a batch of Windows Phone Mango devices, due later this year.