Adele's '21' has become the biggest selling digital album of all time in the US.

The 'Rolling in the Deep' hitmaker took the title from Eminem's 'Recovery' record by selling 1.017 million digital copies of her LP in the country compared to the rapper's 1.005 million sales of his seventh studio album.

Keith Caulfield, Billboard's associate director of charts/retail, said the 23-year-old British singer is "not just a digital phenomenon".

He added: "She appeals to older consumers, who will still buy full albums, and to younger people who may just buy a single track."

According to figures from Nielsen SoundScan, digital sales make up more than 30 per cent of the purchases of '21', which was released in the US in February.

Meanwhile, British rapper Chipmunk, who admitted he would like to collaborate with her one day.

Speaking at the Barclaycard Wireless Festival, he said: "I saw Adele backstage. I would love to work with her, she's from the area I grew up in."

However, he may be in for a disappointment as earlier this year, Adele explained she is not a fan of the musical production that backs rappers' lyrics.

She said: "I love Chipmunk and Tinchy Stryder and that all that lot are doing so well, but I hate that they're having to rap over Swedish dance music - I find it really discouraging."