San Francisco, June 28 : As the tech billionaire Elon Musk celebrates his 51st birthday, his Twitter account has now crossed the mark of 100 million followers, which makes him one of only six people in the world to cross this milestone on the microblogging site. Musk, touted to be the most successful tech entrepreneur and investor in the world, joined the platform in 2009 and now he ranks sixth among the most-followed people including former US president Barack Obama, singer Justin Bieber, and others. Obama is leading with 132.1 million followers, Bieber has 114.1 million, Katy Perry has 108.8 million, Rihanna has 106.9 million and Cristiano Ronaldo has 101.3 million followers on the microblogging site. Meanwhile, Musk, born on June 28, 1971, turned 51 on Tuesday. He often remains in the news for updates on his ventures such as SpaceX, Neuralink, and The Boring Co. He is also known to comment on politics, pop culture and world events. However, Musk, who made a whopping $44 billion deal, has been quiet on the social media platform since June 21. As per Bloomberg Billionaires Index, with an estimated net worth of around $203 billion as of June 2022, Musk is the wealthiest person in the world. In 2002, Musk founded SpaceX of which he serves as CEO and Chief Engineer. In 2004, he was an early investor in electric vehicle manufacturer Tesla Motors, Inc. (now Tesla, Inc.). He became its chairman and product architect, eventually assuming the position of CEO in 2008. Musk helped create SolarCity, a solar energy company, in 2006, which was later acquired by Tesla and became Tesla Energy. In 2015, he co-founded OpenAI, a nonprofit research company promoting friendly artificial intelligence. In 2016, he co-founded Neuralink, a neurotechnology company focused on developing brain-computer interfaces and founded The Boring Company, a tunnel construction company. /IANS