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.