The figures come less than a week after the release of the update, which brings with it a better battery life and several other new features, and the company said response had been "incredibly positive" to the new iPhone 6s.
“Customer response to the iPhone 6s and iPhone 6s Plus has been incredibly positive, we can't wait to get our most advanced iPhones ever into customers’ hands starting this Friday. iOS 9 is also off to an amazing start, on pace to be downloaded by more users than any other software release in Apple’s history,” said Phil Schiller, Apple’s senior vice president of worldwide marketing.
The iPhone 6s and 6s Plus are already available for pre-order online, with Apple last week predicting sales will come in as another record-breaker, beating last year's 10m first-weekend record.
The new phones will go on sale in Apple's shops on 25 September - this Friday.