Monaco, a sovereign city-state on the French Riviera, is known as a "Billionaires' Playground." The tiny city-state is famous for its lavish wealth, casinos, and glamorous events such as the Monaco Yacht Show and the Monaco Grand Prix.

With an area of just 0.78 square miles and a population of 38,300, Monaco is one of the densest countries in the world.

Here are 15 mind-blowing facts about Monaco, from the number of millionaires who live there to the number of police officers per resident.

1. With an area of just 0.78 square miles and a population of 38,300, Monaco is one of the densest countries in the world.

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The tiny city-state is bordered by France and Italy.

2. Monaco is smaller than Central Park in New York City.

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Central Park is about 840 acres or 1.31 square miles in size, making Monaco roughly 60% of the size of the world-famous park.

3. Monaco is home to 12,261 millionaires in less than one square mile.

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The number of millionaires increased by 12% between 2013 and 2018, according to the 2019 Knight Frank Wealth Report.

4. Almost one in three people who live there is a millionaire.

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Business Insider compared the number of millionaires to the number of residents and calculated that more than 32% of the population are millionaires.

5. The average home in Monaco costs $4,560 per square foot.

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That's higher than some of the most expensive housing markets in the world, such as New York City and Hong Kong. In Hong Kong, the average price pre square foot is $2,859, while in Manhattan, real estate costs an average of $1,773 per square foot, according to NeighborhoodX.

For a small one-bedroom apartment in Monaco, buyers can expect to pay at least $1.6 million, Alexander Kraft, chairman and CEO of Sotheby's International Realty France-Monaco, told Mansion Global.

Most "normal" apartments in the city-state cost between $2.2 million and $22.3 million, Kraft said, with the higher end penthouses going for more than $55 million.

And prices are only going up— they've jumped more than 18% since 2017, according to Bloomberg.

6. In 2017, the average home price in Monaco for a resale — not even new construction — was €4.5 million, or more than $5 million.

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In the seaside Larvotto district, one of Monaco's most populous neighborhoods, the average resale price was more than $16 million.

7. Monaco has one police officer for every 100 residents.

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Monaco claims to be one of the most high-security cities in the world, with a 24-hour video surveillance system that covers the entire town.

8. Citizens of Monaco, a city famous for its casinos, are forbidden by law from gambling.

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The gambling ban for residents leaves all the gambling up to tourists and foreign residents.

9. Monaco's GDP per capita is $165,420— the second highest in the world.

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Monaco is beat only by Liechtenstein. Tucked in between Switzerland and Austria, the German-speaking principality has a per capita GDP of $166,021, according to United Nations data.

Liechtenstein is about 80 times larger in area than Monaco.

10. Monaco is one of only four countries in the world with a GDP per capita higher than $100,000.

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11. More than 75% of Monaco's residents are foreign-born.

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Only about 9,259 of Monaco's 38,300 residents were born there, according to the principality's official statistics.

12. Monaco has the highest average life expectancy in the world at 85.8 years.

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Monaco's life expectancy edges out that of San Marino (85 years), Hong Kong (85 years), and Japan (84 years), according to World Bank data.

13. Monaco has a poverty rate of zero.

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14. Monaco is home to one of the world's most expensive streets, which was once the priciest in the world ...

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In 2008, the Wealth Bulletin, a Dow Jones site, named Avenue Princesse Grace the most expensive street in the world, with an average price of $17,750 per square foot.

The street is still one of the most expensive addresses in Monte Carlo, Monaco's most glamorous neighborhood, Edward de Mallet Morgan, a Knight Frank partner who specializes in the high-end residential real estate market worldwide, recently told Mansion Global.

15. ... and it's named for an American Hollywood legend who was also a princess.

Rainier III, Prince of Monaco, and Princess Grace on their wedding day on April 19, 1956, in Monaco.
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Avenue Princesse Grace was named after Grace Kelly, the American Hollywood actress who married Prince Rainier III and took the title Princess of Monaco. After her marriage, the princess gave up acting to focus on charitable and cultural endeavors.

She died in a car accident in Monaco at the age of 52, almost 30 years after she became the Princess of Monaco.