Thanks to over 315 million cumulative iOS devices sold and the breadth of applications available, Apple’s preparing to celebrate their 25 billionth download by awarding the lucky downloader a $10,000 App Store gift card. In only four months, iOS users will have downloaded an additional 7 billion apps from the App Store since last October where Apple reached 18 billion App Store downloads. (15 billion apps were downloaded as of last July). With over 550,000 apps available (175,000 iPad-specific apps) to download, there’s plenty of great applications to choose from that fill a variety of needs on user’s devices. The App Store’s great download spike can also be contributed to the number of iOS devices purchased in 2011 alone: 156 million iOS devices were sold last year compared to a total of 122 million Macs ever sold.

As of today, nearly 25 billion apps have been downloaded worldwide. Which is almost as amazing as the apps themselves. So we want to say thanks. Download the 25 billionth app, and you could win a US$10,000 App Store Gift Card.* Just visit the App Store and download your best app yet.

To participate in the competition, you simply have to purchase or download a free app from the App Store and be the lucky winner randomly chosen by Apple. You can also enter to win without purchasing anything from the App Store by simply visiting the contest page and filling out the linked contest form. One the 25th billion download has been reached, the contest ends! (Each applicable contestant is allowed only 25 entries.)

[via 9to5 Mac]

Edit (02/19/2012): Updated final paragraph to clarify contest rules.