Five million of anything is nothing to sneeze at. Certainly, selling 5 million of something is also rather impressive, but this is precisely what Borderlands 2 has done.
In their latest earnings report, 2K revealed the 5 million units figure to investors. Granted, this may or may not indicate actual units sold to the end consumer, but that's still an impressive figure.
The breakdown between digital and physical copies was not made outside of 2K saying that Borderlands 2 has enjoyed "strong" sales on the digital distribution front.
Fans of the game should also keep an eye on either the Gearbox Software Twitter account or the Borderlands 2 Facebook page. They've been giving out Shift codes throughout the day that unlock skins for each character. These codes will last until November 4. They have already given out three codes, with more still to come!