What does Adele's 21 album now have in common with the soundtracks to Purple Rain and Saturday Night Fever?

As of this week, 21 equals the two soundtracks' 24-week runs at No. 1, as Adele's smash set returns to the top of the Billboard 200 chart.

21 sold 75,000 copies last week, according to Nielsen SoundScan -- about 2,000 copies ahead of the No. 2 album -- Alan Jackson's debuting Thirty Miles West. Adele's album was last No. 1 -- for its 23rd week -- on the tally dated March 17.

21 holds the most frames at No. 1 since Prince & the Revolution's Purple Rain soundtrack also spent 24 weeks atop the list in 1984 and 1985. Only eight albums -- including 21 -- have ruled for at least 24 weeks.

21 has never left the top 10 in its entire 68-week chart run, dropping only as low as No. 7 on the Dec. 10, 2011, chart. It debuted at No. 1 on the March 12, 2011, chart.

It also continues to reign as 2012's best-selling album in the U.S. -- by far. It has sold 3.52 million this year. The second-largest seller is Lionel Richie's Tuskegee, way back in the runner-up slot with 862,000.

21's overall U.S. sales stand at 9.34 million, making it the 24th biggest seller in America since SoundScan began tracking sales in 1991. The biggest album in that span is Metallica's self-titled 1991 album, with 15.78 million sold.