The PlayStation 4 has sold more than 18.5 million systems to consumers worldwide as of January 4, Sony announced, making it the first console maker to reveal its hardware sales success during the usually busy holiday period.

That number includes 4.1 million consoles sold during the "holiday period," which Sony sees as running from November 23 or 24 through January 3 or 4, depending on the region. "I'm liking those numbers" CEO Kaz Hirai said during a CES press conference Monday night, noting that PS4 adoption rates so far exceed those for any other PlayStation product.

Sony last announced shipments of 13.5 million PlayStation 4 systems through the end of September , though perhaps a million or two of those systems may not have sold through to consumers at that point. Given that, PS4 sales seem to have maintained or slightly increased the blistering rate of roughly 2 million sales per month that the system saw during the July to September quarter, based on quarterly reports. That's a pretty good sign for a system that already held a sizable lead in the worldwide "next generation" console sales race, though Sony may have expected more of a sales rate increase during the holiday buying frenzy.

It's hard to put the PS4's fourth-quarter sales in context, though, without holiday sales numbers from the likes of Microsoft and Nintendo. We already know that the Xbox One outsold the PS4 in the US in November, Microsoft's first monthly sales lead in the country since January. The Xbox One also saw some generous bundle deals and a temporary price drop to $350 during the holiday period, suggesting Microsoft could have its own healthy worldwide sales numbers to announce some time soon.

Sony also announced that PS4 owners have bought 81.8 million pieces of digital and retail software worldwide, averaging roughly 4.4 games per system so far. The company also announced that 10.9 million customers were subscribed to PlayStation Plus as of January 2.