Apple's stock took a nosedive this week following the company's earnings report.
The big scary number? 51 million. That's how many iPhones Apple sold in Q4 2013. While it's a record for Apple, it was lower than Wall Street expected (55 to 56 million).
iPhone growth is slowing too, which clearly worried investors. Here's a look at iPhone sales and growth since 2010 from Business Insider Intelligence:
