This Is The Fastest-Growing iPhone Game Ever

Trivia app QuizUp has been on a tear lately.

In just three weeks, the trivia game for iPhone has amassed 3.5 million registered users, New York Magazine reports. On its eighth day, QuizUp reached its 1 millionth user.

Now QuizUp is being hailed as the "fastest-growing iPhone game in history."

QuizUp is a free trivia game for iOS that offers more than 150,000 trivia questions in about 300 categories.

Just last month, QuizUp raised $2 million led by Sequoia Capital and eVentures.