Watch out Apple. On Tuesday, Google's Android boss man Andy Rubin tweeted that half a million Android devices in the world are activated each day, a number that's growing at a rate of 4.4 percent each week. What does that mean for the smartphone market, and how does it compare to Apple? Here, a brief guide, by the numbers:

Over 500,000
Number of Android devices being activated each day, per a tweet from Andy Rubin, Google's senior vice-president of mobile. "Android is blooming in Apple's productless summer," says the International Business Times.

18.1 million
Number of iPhones activated worldwide from January to March. "Apple doesn't announce daily iPhone activations the way Google does, so it's difficult to compare" directly, says Jordan Crook at MobileCrunch, but we can make approximations based on available figures.

Just under 300,000
Estimated number of daily iPhone activations between March 2010 and March 2011, per Crook's calculations. "According to those stats, the iPhone appears to be losing the war on Android — but remember, the iPhone is just one phone," he says. The Android is a platform available across multiple devices, "so it's almost unfair to draw comparisons."

Number of daily Android activations that Google reported in May. Android’s success is clearly accelerating, says Devindra Hardwar at VentureBeat. "Google can thank a continual output of solid Android smartphones from manufacturers for the platform’s growth."

40 percent
Share of the mobile operating-system market that Android should have by the end of 2011, per estimates from the International Data Corporation. "Android is still the operating system to beat," says Matthew Shaer in The Christian Science Monitor. To catch up, "Apple will probably have to release a lower-priced iPhone," something that's already rumored to be in the works.

18.2 percent
Share of the mobile operating system market that Apple iOS, which supports the iPhone, iPad, iPod, and new Apple TV, should have by the end of 2011. But, "while Android has grown in market share, Apple's profit share has eclipsed the rest of the mobile industry," says Sam Oliver at AppleInsider. "One recent analysis showed that Apple could buy rivals Nokia, Research in Motion, HTC and Motorola Mobility all at once with its estimated $70 billion in cash."

Number of daily activations that Android is on track to meet by the end of October, per projections and calculations made by Stefan Constantinescu at IntoMobile

Current U.S. population

More than 800 million
Number of mobile phone users in China

50 percent
Share of smartphones in China that were running Android, as of December 2010, up from in zero in 2009. "Google's Android seems be poised to become the most popular mobile operating system in the world's most populous country," says Bianca Bosker at The Huffington Post.

Approximate population of China, as of 2009

Current world population

Sources: AppleInsider,, Christian Science Monitor,, Huffington Post, International Business Times, MobileCrunch, PC Mag, Twitter, VentureBeat