The Galaxy S4 has reportedly shipped over 20 million units since launch, far more than the previous S3 model. However, these figures are still a bit below analysts expectations of "flying off the shelves."

Multiple Korean news agencies are claiming that Samsung's mobile head had confirmed the 20 million figure, but the company has refused to confirm any reports.

While the S4 is the fastest selling Android smartphone, it still falls short of the iPhone 5's pace.

A rough estimate shows that at 68 days after its launch, the iPhone 5 shipped 23.62 million, the 4S shipped 21.47 million, while the S4 shipped 20 million. The iPhone 4S took 79 days to surpass 32 million shipments and the iPhone 5 reached 34 million shipments in 100 days.