The 20 million figure has been reported by Korean-based news outlet Yonhap News, but has not officially been confirmed by Samsung.
The milestone refers to global channel sales of the Galaxy S4 rather than how many devices are actually in the hands of consumers, but it's still a hugely impressive figure.
The 20 million number means that Galaxy S4 sales are approximately 1.7 times faster than sales of Samsung's previous Galaxy S III at the same point in the product life cycle, according to Yonhap News.
Samsung revealed back in May that it had shipped 10 million Galaxy S4 smartphones globally, less than a month after the smartphone was launched.
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