Answer by taking a quote from the following article:

Percy Tyrone Sledge (November 25, 1940 - April 14, 2015) was an American R&B, soul and gospel singer. He is best known for the song "When a Man Loves a Woman", a No. 1 hit on both the Billboard Hot 100 and R&B singles charts in 1966. It was awarded a million-selling, Gold-certified disc from the RIAA. Having previously worked as a hospital orderly in the early 1960s, Sledge achieved his strongest success in the late 1960s and early 1970s with a series of emotional soul songs.

Sledge was born on November 25, 1940, in Leighton, Alabama. He worked in a series of agricultural jobs in the fields in Leighton before taking a job as an orderly at Colbert County Hospital in Sheffield, Alabama. Through the mid-1960s, he toured the Southeast with the Esquires Combo on weekends, while working at the hospital during the week. A former patient and mutual friend of Sledge and record producer Quin Ivy introduced the two. An audition followed, and Sledge was signed to a recording contract.  Sledge's soulful voice was perfect for the series of soul ballads produced by Ivy and Marlin Greene, which rock critic Dave Marsh called "emotional classics for romantics of all ages". "When a Man Loves a Woman" was Sledge's first song recorded under the contract, and was released in March 1966. According to Sledge, the inspiration for the song came when his girlfriend left him for a modelling career after he was laid off from a construction job in late 1965, and, because bassist Calvin Lewis and organist Andrew Wright helped him with the song, he gave all the songwriting credits to them. It reached No. 1 in the US and went on to become an international hit. When a Man Loves a Woman" was a hit twice in the UK, reaching No. 4 in 1966 and, on reissue, peaked at No. 2 in 1987. The song was also the first gold record released by Atlantic Records. The soul anthem became the cornerstone of Sledge's career, and was followed by "Warm and Tender Love" (covered by British singer Elkie Brooks in 1981), "It Tears Me Up", "Take Time to Know Her" (his second biggest US hit, reaching No. 11; the song's lyric was written by Steve Davis), "Love Me Tender", and "Cover Me".  Sledge charted with "I'll Be Your Everything" and "Sunshine" during the 1970s, and became an international concert favorite throughout the world, especially in the Netherlands, Germany, and on the African continent; he averaged 100 concerts a year in South Africa.

How long did the song stay at No. 1?