Facts about Britain's record-breaking Queen Elizabeth II

Queen Elizabeth II meets well wishers during a walkabout close to Windsor Castle as she celebrates her 90th birthday, in Berkshire, England, Thursday, April 21, 2016. (John Stillwell/Pool Photo via AP) (The Associated Press)

Britain's Queen Elizabeth II waves to the crowd as she rides in an open top car with Prince Phillip to celebrate her 90th birthday in Windsor, England, Thursday April 21, 2016. The queen was born Princess Elizabeth on April 21, 1926, and became queen at 25 upon the death of her father, King George VI, in 1952. A majority of Britons have lived under no other monarch. (AP Photo/Alastair Grant) (The Associated Press)

Queen Elizabeth II meets well wishers during a walkabout close to Windsor Castle as she celebrates her 90th birthday, in Berkshire, England, Thursday, April 21, 2016. (John Stillwell/Pool Photo via AP) (The Associated Press)

On Thursday, Queen Elizabeth II became first British monarch to reach the age of 90. It's just one of many milestones the queen has marked in her nine decades. Here's a look at some other numbers regarding Britain's queen:

— Elizabeth has reigned for 64 years and 75 days. On September 9, 2015, she became Britain's longest-reigning monarch, passing her great-great-grandmother Queen Victoria.

— She is the world's oldest monarch since the death of Saudi Arabia's King Abdullah last year.

— She has had 12 British prime ministers serve during her reign, from Winston Churchill to David Cameron.

— She has met 12 U.S. presidents, from Herbert Hoover (after he had left office) to Barack Obama — more than a quarter of all the U.S. presidents since Independence. The only president during her reign that she did not meet was Lyndon B. Johnson.

— She has traveled more than 1 million miles (1.6 million kilometers) on official trips, visiting 106 of the 193 current official members of the United Nations.

— She has visited Canada 22 times — the largest number of trips to any nation.

— She has four children, eight grandchildren and five great-grandchildren.

— She has cut back on her official duties in the last few years, but Elizabeth still conducted 177 official engagements in the last year.