His breakout hit "Gangnam Style", which debuted in July 2012, has become the most watched video on YouTube, with more than 2.1 billion views.

The staggering number has caused YouTube to upgrade its system.

"We never thought a video would be watched in numbers greater than a 32-bit integer" (2,147,483,647 views), the company said.

"But that was before we met Psy."

YouTube and Google marked the occasion with a special feature on the original video.

If viewers go to the YouTube page where "Gangnam Style" lives and put their cursors over the 2 billion play count, the number counts backwards, then forward, in rapid succession.