Mukesh Ambani again tops 90 Indian billionaires, 28 of them newcomers, on Forbes' annual ranking as Bill Gates emerged as the world's richest person for the 16th time in the last 21 years.

With a current net worth of $79.2 billion, up from $76 billion in 2014, Gates for the second consecutive year beat out telecom mogul Carlos Slim Helu (No. 2), whose net worth increased to $77.1 billion from $72 billion last year, according the US magazine's annual ranking of the world's billionaires released Monday.

Warren Buffett (No. 3) moved up one slot, with a net worth of $72.7 billion, ahead of Spanish clothing retailer Amancio Ortega (No. 4), best known for the Zara fashion chain, who increased his net worth $500 million for a total of $64.5 billion.

Oracle's Larry Ellison (No. 5) remained in the fifth spot; his net worth increased to $54.3 billion.

Thanks to the tech boom and a strong dollar in the currency markets, the US led with the greatest number of billionaires, with 536, followed by China with 213, Germany with 103, India with 90 and Russia with 88.

California has 131 billionaires, more than any country besides the US and China.

This year, 290 billionaires were new to the list, another record number, beating out a prior high of 268 newcomers in 2014.

China had the most newcomers, adding 71 to the list. Fifty seven newcomers were from the US, 28 from India, and 23 from Germany.

Indian billionaires include: 39. Mukesh Ambani ($21 billion); 44. Dilip Shanghvi ($20 billion); 48. Azim Premji ($19.1 billion); 66. Shiv Nadar ($14.8 billion); 69. Hinduja Brothers ($14.5 billion); 82. Lakshmi Mittal ($13.5 billion); 129. Ananda Krishnan ($9.7 billion); 142. Kumar Mangalam Birla ($9 billion); 185. Uday Kotak ($7.2 billion), 208. Gautam Adani ($6.6 billion), 208. Sunil Mittal and family ($6.6 billion), 208. Cyrus Poonawalla ($6.6 billion), 254. Desh Bandhu Gupta ($5.8 billion); 283. Savitri Jindal and family ($5.3 billion).

A record 1,826 billionaires (up from 1,645 in 2014) made the list, with an average net worth of $3.86 billion (down $60 million from $3.92 billion in 2014).

Added together, the total net worth for this year's billionaires was $7.05 trillion, up from $6.4 trillion last year.

Regionally, Asia-Pacific boasted the most billionaires, with 562 billionaires, followed by the US with 536 and Europe with 482.

Compared to last year's list, Mark Zuckerberg (No. 16), with a net worth of $33.4 billion, made it into the top 20 for the first time.

The biggest net worth gainer was Warren Buffett (No. 3), whose fortune increased by $14.5 billion for a total net worth of $72.7 billion.

Buffett's Class A Berkshire Hathaway stock eclipsed $200,000 per share for the first time and continued to climb.

A record number of women made the list this year: 197 versus 172 in 2014, representing an increase of 15 percent. Twenty nine of these women are self-made billionaires.

A notable newcomer included is the world's youngest billionaire, Evan Spiegel (No. 1250), age 24, of the US, with a net worth of $1.5 billion.