By now, you’ll likely be aware of Apple’s announcement yesterday of some iOS milestones, just in time to steal some attention away from the first day of CES – not least rival Samsung’s press conference.

The key figures: 40bn iOS app downloads so far, with nearly 20bn of them coming in 2012, and 2bn in December alone. There are now 500m active App Store accounts – an important number – and Apple has paid out $7bn to app developers since the store’s launch in 2008.

So let’s dig into that $7bn figure. Apple announced in June that it had paid out $5bn to developers, so $2bn in seven months since then means around $285.7m a month. Factor in Apple’s 30% cut of app sales and in-app purchases, and you get (roughly) $408m of gross App Store revenues a month.

That’s an annual run-rate of $4.9bn from iOS apps alone – a figure that doesn’t include advertising.

Back to that 500m active App Store accounts figure too, which is worth thinking about. That’s a true measure of the global reach of iOS across the various devices: people who own, say, an iPhone and iPad will only be counted once.

That means this is a more valuable number than simply counting historic iOS device sales when gauging the potential market for iOS apps. Now, it’d be good to see a similar active-user (as opposed to activated devices) stat for Android as a comparison.