Remember how Paul McCartney sang, "Will you still need me, will you still feed me, when I'm 64?" McCartney found out Sunday when he turned that age.

The legendary musician wrote in the "Beatles Anthology" that he actually wrote "When I'm Sixty-Four" when he was 16, hoping maybe someday he'd get a career in musical comedy and be able to use that song.

John Lennon was quoted in the "Anthology" as saying The Beatles would sing that song around the piano in their Cavern Club days when they burned out their amps.

The two musicians eventually shared song credit for the tune.

George Martin wrote in the "Anthology" that it was a dreadful mistake not to put "When I'm Sixty-Four" as the B-side to either "Strawberry Fields Forever" or "Penny Lane."

McCartney's kids told him in the fall that he should lie low because of all the awful media references that will come out for this birthday.

McCartney is going through a divorce with Heather Mills McCartney that's being dragged through the British tabloids.

However, he's still known as rock's first billionaire and his tour was one of the top-grossing concert series of 2005.

Nicknamed "Macca," the rocker was born James Paul McCartney on June 18, 1942 in Liverpool, Merseyside, England.

McCartney had four children with his wife, Linda Eastman, whom he was married to from 1969 to her death in 1998.

McCartney married Mills in 2002, and they had a daughter in 2003.

Mills and McCartney announced their separation last month.