London, England (CNN) -- More than a sixth of the British population can expect to live to their 100th birthday, a prospect that will put a strain on the pension system, the British government said Thursday.
In addition, by 2066, there will be at least half a million people older than 100 -- including 7,700 "super-centenarians" older than 110, the Department for Work and Pensions said.
More than 10 million people currently living in the United Kingdom, or 17% of the population, will live to be 100, the department said.
Three million of them are currently younger than 16; 5.5 million are between the ages of 16 and 50; and 1.3 million are between 51 and 65, the department said. Around 875,000 are already older than 65, it added.
"These staggering figures really bring home how important it is to plan ahead for our later lives," said Pensions Minister Steve Webb. "Many millions of us will be spending around a third of our lives or more in retirement in the future."
Reforming the pension system to make it sustainable for the long-term, ensuring a "decent" state pension, and helping people save in a pension connected to the workplace are all priorities, he said.
The department said it has a "Centenarian Clerk" who works with Buckingham Palace to make sure every 100-year-old in Britain receives a birthday card from Queen Elizabeth.
"He will be very busy in 2066!" the department said.
The figures are based on population projections and life expectancy estimates from the Office for National Statistics.