Age is just a number. But that number is on the move, and longevity is on its way to running up the score. According to the United Nations, in 1990 there were 95,000 people on the planet who made it to 100. Today there are more than 500,000 centenarians, and, by 2100, it’s projected there will be more than 25 million. In 1980, around 382 million people were 60 and older. By 2050, that number will exceed 2 billion. There are some gerontologists who believe the first person to live to age 150 has already been born.