Sony has announced global Killzone Shadow Fall sales of over 2.1 million.
That accounts for both physical retail "sell-in quantities" and digital PlayStation Store sales combined, as of January 15, 2014.
With Sony having claimed 4.2 million PS4 sales by the end of 2013, this would indicate that almost half of all PS4 owners have picked up a copy of the Guerrilla Games first-person shooter.
"I am thrilled that so many users have been enjoying Killzone Shadow Fall since the launch of PS4," commented president of Sony Computer Entertainment Worldwide Studios Shuhei Yoshida in the press release. "This title fully embraces the creativity of the development team at Guerrilla Games based in the Netherlands, and is a great representation of what SCE WWS has to offer.
"SCE will continue to deliver exciting software titles, and is currently developing more than 30 titles including Driveclub, inFAMOUS Second Son and The Order: 1886, which offer entertainment experiences only possible on PS4."
The announcement also notes that release dates for Guerrilla's upcoming Killzone Shadow Fall DLC "will be announced shortly".
That includes two multiplayer maps, 'The Cruiser' and 'The Hangar', which will be free to all players, and a multiplayer 'DLC expansion pack' which has yet to be detailed fully.
The developer also plans to introduce a clan system to Killzone Shadow Fall via an update due for an 'early February' release.