London - On Monday, Queen Elizabeth II marks her Sapphire Jubilee, becoming the first British monarch to reign for 65 years. It's just one of many milestones the queen has marked in her nine decades. Here are some other significant numbers about her record-breaking life and reign:— Elizabeth assumed the throne on the death of her father, King George VI, on Febuary 6, 1952. On September 9, 2015, she became Britain's longest-reigning monarch, passing her great-great-grandmother, Queen Victoria.— She turned 90 on April 21, 2016, and has been the world's oldest monarch since the death of Saudi Arabia's King Abdullah in 2015.— She has had 13 British prime ministers serve during her reign, from Winston Churchill to Theresa May.— She has met 12 US presidents, from Herbert Hoover (after he had left office) to Barack Obama — more than a quarter of all the US presidents since Independence. The only president during her reign that she did not meet was Lyndon B. Johnson. She is due to meet President Donald Trump when he comes to Britain for a controversial state visit later this year.— She has traveled more than 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 past few years, but Elizabeth still conducted 341 official engagements in 2015.