• Elon Musk, who had his first child at 29 years of age, confirmed he has 9 kids with 3 women.

• He told The Full Send podcast that a low birth rate was the biggest threat facing the world.

• Mark Cuban had asked Musk how many kids he'd have, to which he replied: "Mars needs people."

Elon Musk has confirmed he has nine kids with three women and would rather "civilization went out with a bang than a whimper and adult diapers."

Speaking on The Full Send podcast released on Thursday, Musk was asked how many children he has and said he has nine offspring with three women. One of the hosts mentioned he had met Musk's twins, who are now going to college, their father said.

The world's richest individual said the biggest threat facing the world was a flatlining birthrate and claimed that overpopulation was a myth.

"Population is not growing. Lifespan is increasing. People are living longer. That's the only reason why the population on earth hasn't plummeted, but it will plummet," Musk said.

However, the United Nations expected the world's population to rise by 2 billion over the next 30 years, from 7.7 billion to 9.7 billion by 2050.

Musk added: "One thing to track is the ratio of adult diapers to baby diapers. What point does the country have more adult diapers and baby diapers?" He said sales of adult diapers in Japan have outpaced those for babies since 2011.

Musk has long shared his concerns about a declining birthrate. The SpaceX CEO wants to put humans in a settlement on Mars. He previously said on a podcast that SpaceX will put humans on the planet with its Starship rockets in five to 10 years.

However, he claimed there would not be enough people to move to Mars if the demographic crisis continued.

In this week's podcast, Musk says civilization will die with a whimper and adult diapers: "That kind of sucks doesn't it, it's like anticlimactic. Frankly, if given the choice, I'd rather civilization went out with a bang than a whimper and adult diapers."