Billionaire investor Warren Buffett said long-term investors of Apple's stock shouldn't obsess with near-term iPhone sales.

"The idea that you're going to spend loads of time trying to guess how many iPhone X ... are going to be sold in a three-month period totally misses the point," the Berkshire Hathaway chairman and CEO said in a "Squawk Box" interview that aired Friday. "It's like worrying about the number of BlackBerrys 10 years ago."

Buffett revealed that Berkshire bought an astounding 75 million shares of Apple during the first quarter. That adds to the 165.3 million shares Berkshire already owned at the end of 2017.

As of Thursday's closing price of $176.89 per share, Berkshire's Apple stake was worth about $42.5 billion. Berkshire is now the third largest Apple shareholder, behind Vanguard and BlackRock.

Apple has "a wide, wide gap. I mean it's an amazing business," Buffett told CNBC's Becky Quick. "You can put all of their products on a dining room table."

"Nobody buys a farm based on whether they think it's going to rain next year," he added. "They buy it because they think it's a good investment over 10 or 20 years."

Berkshire first made an investment in Apple in 2016 after a person at the firm bought about 10 million shares. Buffett then looked at the stock and purchased considerably more, the billionaire recalled in August to CNBC.

Apple reported quarterly earnings this week that beat expectations but sold fewer iPhones than expected. Still, the number of iPhones sold appeared to calm investors about a potential slowdown in sales and speculation that Apple might be looking to wind down the iPhone X.

The tech giant late Tuesday also increased its quarterly dividend by 16 percent and announced a $100 billion buyback program.

In his CNBC interview, Buffett also said he believes the economy is growing faster than 2 percent. "The last seven or eight years have averaged 2 percent roughly," he pointed out. "It's stronger than that right now."

Buffett spoke to CNBC on Thursday evening from Omaha, Nebraska, where tens of thousands of Berkshire shareholders were gathering for Saturday's annual meeting.

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