Washington, Oct 18 (IANS): Though Apple iPhone 4S failed to wow pundits when it was unveiled, the company sold more than 4 million units over the weekend, making it the fastest-selling iPhone ever.

More than 25 million people have also downloaded iOS 5 to their iPhones, iPads and iPod Touches in the five days since the operating system's release, the technology giant announced Monday.

And more than 20 million people have signed up for iCloud, Apple's free service that syncs data such as calendars, contacts and photos wirelessly across a user's computer and portable Apple gadgets, the company said. The service was also launched five days ago.

iPhone 4S sales were "more than double the iPhone 4 launch during its first three days", Philip Schiller, Apple's senior vice president of worldwide product marketing, said in the company announcement.

The previous-generation iPhone 4, launched in June 2010, is Apple's bestselling product; more of the devices have been sold than all earlier versions of the iPhone combined.

More than 1 million iPhone 4S handsets were pre-ordered in the first 24 hours after the new product was revealed Oct 4, the day before Apple co-founder and technology icon Steve Jobs died.

So far, the iPhone 4S is for sale in the US, Canada, Australia, France, Germany, Japan and Britain. Apple said it will be available in 22 additional countries Oct 28 and in more than 70 countries by the end of the year.