Written and produced by Tricky Stewart and The-Dream, with additional writing by James Bunton and Corron Ty Cole, "Leavin'" was sent to U.S. mainstream radios on March 10, 2008.

[1] Namesake of the album's title, "Leavin'" was considered a departure from McCartney's youthful image in favor of adult-oriented subject matter, vocal delivery and production.

Lyrically, the song finds McCartney admiring a female's backside with plans to steal her from her current beau.

Sonically, the song is pop with an electro production style and sound effects from digital watches, alarm clocks and kitchen timers.

"Leavin'" remains McCartney's biggest hit single in the United States, reaching number one on the Billboard Top 40 Mainstream and peaking within the top ten on the Billboard Hot 100; it sold over 3 million digital downloads and received triple platinum certification by Recording Industry Association of America (RIAA).

"[2] He also revealed that the album is "certainly a little bit more urban-influenced, I worked with people really well known in that area of music, they gonna see a lot of growth, obviously with the first single.

[7] Written in the key of A major,[8] it has a tempo of 79.255 beats per minute, with McCartney's vocals spanning from the low-note of E4 to the high-note of C6.

[9] Lyrically, "Leavin'" sees the singer eyeing a female's backside with plans to steal her from her current beau.

Nick Levine of Digital Spy gave the song 4 out of 5 stars, writing that 'Leavin' "is the musical equivalent of McCartney's first tuft of chest hair, a hard-edged crunk gem that wouldn't sound out of place on an Usher or Chris Brown album.

Combining smooth, radio-friendly choruses with trendy electro production from Tricky and The Dream, it makes McCartney sound fresh and a little bit sexy without scaring off the milk 'n' cookies brigade.