(Bloomberg) -- Like many women her age, Kylie Jenner is active on social media. But she’s done one thing that no one else has: build a billion-dollar fortune by age 21.

Jenner is the youngest person to become a billionaire with her own company, Kylie Cosmetics, and she has several other young billionaires to thank.

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“The business would not exist at its current size without social media,” said Conor Begley, co-founder of brand-marketing company Tribe Dynamics.

Instagram co-founder Kevin Systrom, Snapchat co-founder Evan Spiegel, Facebook co-founder Mark Zuckerberg and Twitter co-founder Jack Dorsey are all billionaires younger than 45.

Each of Jenner’s Instagram posts is worth about $1 million, according to Hopper HQ, a social media scheduler. Jenner’s posts include family photos and mirror selfies, in addition to new product announcements or promotions for blush, lip gloss and eye shadow. Jenner has 128 million followers on Instagram, and plenty of others on Twitter, Facebook and Snapchat.

“She’s a unique case in that she has a massive, massive audience,” Begley said. “That can be replicated for sure.”

Take Rihanna (68.3 million Instagram followers), whose Fenty Beauty has partnered with luxury-goods powerhouse LVMH, and Huda Kattan (33.6 million followers), who left a finance job to become a makeup artist. She founded Huda Beauty with her sisters in 2013 after her makeup blog became popular. The company now has $200 million in annual revenue, according to Begley.

“What you find consistently across the successful celebrity brands is a deep passion and authenticity by the celebrity for the creation of the products themselves,” Begley said. “Kylie is very active in the development of her products and can show her fans that process, day-to-day, through Instagram. That level of visibility and commitment makes her fans significantly more likely to support her.”

To contact the reporter on this story: Sophie Alexander in New York at salexander82@bloomberg.net

To contact the editors responsible for this story: Alan Goldstein at agoldstein5@bloomberg.net, Peter Eichenbaum, Steven Crabill

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