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The Samsung Galaxy S4 LTE-A comes with the powerful Qualcomm Snapdragon 800 SoC rather than the Snapdragon 600 that powers the international version, but is otherwise identical to its predecessor. The international variant comes with a 5-inch 1080p Super AMOLED display, 2 GB of RAM, 13 megapixel rear camera, 32 GB in-built memory, microSD card slot and IR port.
The fact that Samsung Galaxy S4 LTE-A is able to make use of the SK Telecom's new super-fast network speeds and equally well supported by the Samsung's strong marketing campaign has certainly helped push those sales numbers so high.
Source: GSMArena