Obama meets his favourite rapper, Kendrick Lamar

Kendrick Lamar (AAP, file)
Kendrick Lamar (AAP, file)

When asked what his favourite tune of 2015 was, US President Barack Obama's answer was Kendrick Lamar's 'How Much a Dollar Cost'.

Recently, the pair met at the White House's Oval Office to promote the Pay It Forward programme, a mentoring service for inner-city youth, with the rapper now opening up about his conversation with Obama, Rolling Stone reports.

"I look at where I'm at today and realise that most of my success is owed to the mentors that was in my life," Lamar says in the Pay It Forward video.

"I sat down with President Barack Obama and shared the same views. Topics concerning the inner cities, the problems, the solutions, and furthermore embracing the youth, both being aware that mentoring saves lives."

Obama's senior adviser Valerie Jarrett shed some more light on the president's encounter with Lamar in an interview with Buzzfeed. "You know what the president said to him," Jarrett said. "[Because Lamar] was a little nervous — bless his heart, he's really a very nice young man, and the president said, 'Can you believe that we're both sitting in this Oval Office?'"

Watch the video.