KYLIE Jenner showed off her famous bum as she partied with sisters Kim, Kourtney and Khloe in Santa Monica last night.

The famous foursome enjoyed an evening out at the posh Giorgio E Baldi Italian restaurant.

Kylie, 21, wowed in a form-fitting taupe dress, while her siblings rocked equally revealing outfits.

Hopefully it was Kylie who was picking up the bill while out with her millionaire sisters – she recently became the youngest billionaire at the age of just 21.

Business mag Forbes ranked her as the world’s 2,057th richest person with a net worth of $1billion (£760million). She has become a billionaire two years younger than Zuckerberg, who reached the feat aged 23 in 2008.

Jenner, speaking to Forbes, said: “I didn’t expect anything. I did not foresee the future.

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“But (the recognition) feels really good. That’s a nice pat on the back.”

Her fortune comes from Kylie Cosmetics, the makeup company she runs largely from her iPhone, with the help of her “momager” mother, Kardashian matriarch Kris.

Shrewd Kris, 63, manages all her children’s financial operations for a ten per cent cut. Forbes estimated that the cosmetics company, which is 100 per cent owned by Jenner, made £274million in sales last year.

Jenner’s initial stock of £22 “lip kits” – with matching lipstick and lip liner – sold out in less than a minute, crashing the website.

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Most of Kylie Cosmetics’ sales come directly from the social media accounts of Jenner, who is currently dating high-profile US rapper Travis Scott.

She has 128 million followers on Instagram, around three-quarters of whom are estimated to be aged between 18 and 24.

Jenner, who made her reality TV debut aged ten, also has one of the most viewed accounts on Snapchat and is followed by 26.7 million on Twitter. When she tweeted that she was “sooo over” Snapchat last year, more than £760million was wiped off the company’s stock market value.

Jenner said: “Social media is an amazing platform. I have such easy access to my fans and my customers.”