What a week for Mumford & Sons.

The British band's sophomore release, "Babel", moved a whopping 600,000 copies in its first week, according to Nielsen SoundScan, marking the biggest debut sales week of the year. It easily scores the group its first No. 1 on the Billboard 200 and the first for its label, Glassnote Records. (Even more stunning: "Babel" outsells the Nos. 2-8 albums on the Billboard 200 combined.)

However, a number of media outlets and pundits have done a double-take about "Babel's" sales, stunned by the album's popularity and mystified as to how the band could have sold so much. After all, "Babel" sold 225,000 more in its first week than the album that previously owned the record for the largest debut this year: "Believe", by the ubiquitous Justin Bieber.

But "Babel" did what sophomore albums are supposed do: fulfill the promise of a solid-selling debut set. "Sigh No More", the act's first album, has moved 2.5 million in the United States and has remained on the Billboard 200 since it debuted on March 6, 2010. The set, which peaked at No. 2, hasn't left the top 75 since July 2010. Certainly, one would think a significant chunk of those 2.5 million fans turned up in the first week to buy "Babel". Further, the band appeals to a broad demographic of fans (college kids, older NPR listeners, alternative rock radio listeners) who still want the experience of an album. Mumford is anything but a Flo Rida-like track-oriented act.

That said, here are some impressive statistics related to the first sales week of "Babel":

Largest debut sales week of 2012: With 600,000 sold, "Babel" easily trumps the first week racked by Bieber's "Believe"(374,000), which owned the largest debut of the year until now. Believe falls to second place in terms of 2012's biggest starts, followed by Madonna's "MDNA" (359,000) and P!nk's "The Truth About Love" (280,000).

Biggest sales week for a rock album since 2008: The album notches the best week for a rock set since AC/DC's "Black Ice" bowed at No. 1 with 784,000 on Nov. 8, 2008.

Mumford & Sons have scored four top 10 singles on the Alternative airplay chart, and their current single, "I Will Wait," reaches No. 1 on the Rock Songs airplay tally this week. "Sigh No More" spent six weeks atop the Rock Albums chart and has been a near-­constant presence on the tally since it was released in February 2010.

Biggest sales week for RED Distribution: "Babel's" bow garners RED Distribution its largest sales week. It surpasses the 394,000 racked by Bone Thugs-N-Harmony's "The Art of War" (Ruthless/Relativity) when it debuted at No. 1 on Aug. 16, 1997. ("Babel" was released on Gentlemen of the Road/Glassnote Records and distributed by RED, Sony's indie distribution arm.)

"Babel" is RED's first No. 1 since Radiohead's "In Rainbows" (TBD/ATO) jumped to the top of the list (flying from No. 156 to No. 1) on Jan. 12, 2008. RED will continue to shine in the coming weeks, as the company prepares to release Jason Aldean's new album, "Night Train", on Oct. 16. His last release, "My Kinda Party", has spent 100 weeks on the Billboard 200 and shifted 2.8 million in the United States.

Second-largest sales week of 2012 (overall): "Babel's" big debut is the overall second-largest this year, in terms of copies sold in a single week, behind Adele's "21". The latter moved 730,000 in the week after Adele's multiple Grammy Award wins this year.

Second-largest sales week for an independently distributed album in SoundScan history: Only one other indie-distributed set in SoundScan history (1991-present) has sold more in a week: the Eagles' Walmart-exclusive "Long Road Out of Eden". It bowed with 711,000 copies at No. 1 on Nov. 17, 2007.

Second-largest digital sales week for an album: With 420,000 downloads sold, "Babel" scores the second-biggest frame for a digital album. Only Lady Gaga's "Born This Way", which moved 662,000 downloads in its first week in 2011, sold more digital copies in a week. (A chunk of Lady Gaga's figure was driven by Amazon MP3's sale pricing of the set at 99 cents for two days during release week.) In third place on the list of the all-time biggest download weeks is Lil Wayne's "Tha Carter IV", which sold 362,000 digital copies during its first week last year.

Sixth straight year an indie album has hit No. 1: Since 2007, there has been at least one independently distributed album that has ruled at No. 1. "Babel" is the first such indie set this year. It follows Cake's "Showroom of Compassion" and Mac Miller's "Blue Slide Park" in 2011. In 2010, three indie sets topped the list, while there was one each in 2009, 2008 and 2007.