Following rumors over the weekend that the 3G-enabled iPad was estimated to have sold 300,000 units since its debut on Friday, Apple has come forward with news that all models of the iPad combined have topped one million units sold.

AppleInsider is reporting that the iPad has reached a milestone on Friday with the launch of the iPad 3G: In just 28 days since the hardware was first released on April 3rd, the company has sold one million units.

“One million iPads in 28 days — that’s less than half of the 74 days it took to achieve this milestone with iPhone,” proclaimed Apple CEO Steve Jobs in Monday’s statement out of Cupertino. “Demand continues to exceed supply and we’re working hard to get this magical product into the hands of even more customers.”

In addition to the one million units sold, Apple revealed that those new iPad users have already downloaded more than 12 million apps from the App Store and a whopping 1.5 million e-books from the new iBookstore.

New applications created specifically for the iPad now number more than 5,000, which is on top of the more than 200,000 apps already in the App Store written specifically for the iPhone and iPod touch.

Weekend estimates from analysts pegged the new 3G-equipped iPad at about 300,000 units sold (including preorders), although it’s not clear if that number is factored into Apple’s announcement, which only includes units sold through last Friday. The Wi-Fi only iPad took just five days to hit 450,000 devices sold, so it’s likely that the 3G model will help Apple get to the next million even quicker than the first.

Apple has been caught off guard by strong sales of the iPad, which has forced the company to delay its international debut by one month so the manufacturing can catch up to the demand.