The music video for South Korean singer Psy's Gangnam Style exceeded YouTube's view limit,
prompting the site to upgrade its counter. YouTube said the video - its most watched ever -has been viewed more than 2,147,483,647 times.
It has now changed the maximum view limit to 9,223,372,036,854,775,808, or more than nine quintillion.
Gangnam Style became a worldwide hit when it was released in 2012, largely due to the surreal video. The second most-watched video on YouTube - Baby by Justin Bieber - lags behind Gangnam Style by more than a billion views.

How do you say 9,223,372,036,854,775,808?
Nine quintillion, two hundred and twenty-
three quadrillion, three hundred and seventy-
two trillion, thirty-six billion, eight hundred
and fifty-four million, seven hundred and
seventy-five thousand, eight hundred and
eight.
Gangnam Style has been watched more than 2.15 billion times as of 4 December YouTube's counter previously used a 32-bit integer, which is a unit used to represent data in computer architecture. This means the maximum possible views it could count was 2,147,483,647. On 1 December, it posted a statement saying: "We never thought a video would be watched in
numbers greater than a 32-bit integer... but that
was before we met Psy."
Google, which owns YouTube, later told website The Verge that engineers "saw this coming a couple months ago and updated our systems to prepare for it". YouTube now uses a 64-bit integer for its video
counter, which means videos have a maximum
viewer count of 9.22 quintillion. Psy has yet to comment although news of YouTube's change was posted on his Facebook
and Twitter pages.

source- http://m.bbc.com/news/world-asia-30288542?OCID=fbasia