WASHINGTON (AP) — A few hours after President-elect Donald Trump was briefed by intelligence officials about Russian meddling in the election, an Associated Press reporter called his cellphone seeking an interview.

The call went to voicemail and the reporter did not leave a message. About an hour later, Trump called back.

It's hard to imagine many politicians — particularly one about to become president of the United States — calling back an unknown number on their cellphone.

With Trump, it's simply how business gets done, whether he's fielding calls from real estate partners and longtime friends or foreign leaders and congressional lawmakers in the weeks after the election.

But as Trump prepares to take the oath of office Friday, the future of his ever-present Android smartphone is now a matter of national security. On Thursday, he told a friend that he had given up his phone, as security agencies had urged him to do. It was unclear whether he was following the lead of President Barack Obama, the nation's first cellphone-toting president, who exchanged his personal device for a Blackberry heavily modified for security purposes.

The friend who spoke with Trump spoke to The Associated Press on the condition of anonymity in order to disclose the private conversation.

The presidency has long been a lonely, isolating office, with security concerns keeping the commander in chief at a distance from the public. Under Obama, worries about cyber intrusions — particularly by foreign governments — pulled the president's technology deeper into the security bubble as well. Many of the functions on Obama's Blackberry were blocked and only a handful of people had his phone number or email address.

Trump doesn't email, but he uses his phone to tweet — something he's made clear he plans to continue in office. He's known to make calls early in the morning and late at night, often seeking input from multiple sources when making a decision. Sometimes he leaves a voicemail.

Christopher Ruddy, the CEO of Newsmax and a friend of the president-elect, described Trump's phone etiquette, as "just like one of his speeches, it's very stream of consciousness."

Sen. Bob Corker, R-Tenn., called Trump "amazingly accessible," saying the president-elect picks up his phone even when he doesn't know who is calling.

"My phone says, No Caller ID, so I'm not saying that it has anything to do with me," Corker said. "Nobody knows who it is that's calling when I'm calling."

Foreign leaders and diplomats took advantage of Trump's accessibility in the days after his election as they scrambled to find ways to reach him. Some called into Trump Tower hoping to be transferred to the president-elect's office. Australian Prime Minister Malcolm Turnbull got Trump's cellphone number from the golfer Greg Norman.

Trump's accessibility can create headaches for his aides, who can't always control who he's speaking to or what he's saying. After actress Meryl Streep blasted Trump during a Golden Globes speech earlier this month, a New York Times reporter called the president-elect at midnight to get a response. Trump's criticism of Streep dominated the news the following day, overshadowing his team's planned agenda.

For Obama, getting to use a Blackberry in office was considered a victory. He later switched to an iPhone that allowed him to send and receive email from a limited group of people, surf websites and read the news.

But Obama wasn't known to use his cellphone to make or receive telephone calls, according to individuals familiar with his technology use. Even senior government officials didn't have the number and instead reached the president through the White House switchboard.

The president also used the switchboard to place his calls, said the individuals, who weren't authorized to speak publicly and requested anonymity.

Obama had a phone in his control that he used to tweet, one of the only devices with access to the official presidential Twitter feed due to hacking concerns. But Obama rarely hit "send" on a tweet himself, and never without coordinating it with his staff, the individuals said.

If Trump does get rid of his cellphone, it could end up with a home not far from the White House.

Curators at the Newseum, which chronicles the First Amendment and the evolution of electronic communication, reached out to Trump's campaign in November about the prospect of acquiring his Android phone. They haven't heard back, said Carrie Christoffersen, the museum's curator of collections.

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AP writers Julie Bykowicz, Josh Lederman and Ben Nuckols contributed to this report.

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Follow Julie Pace at http://twitter.com/jpaceDC