Video: 660 Investitures and 23,816 days on the throne: The Queen in numbers

As the Queen celebrates her 91st birthday on April 21, here's a look at Elizabeth II's life and reign in numbers.

As the Queen celebrates her 91st birthday, here's a look at Elizabeth II in numbers.

The Queen and Prince Philip at the Giants Causeway

The Queen and Prince Philip at the Giants Causeway

:: 1 - ranking in the list of world's longest-serving current monarchs. She moved to first place after the death of the King of Thailand in 2016.

:: 3 - number of dogs the Queen has left - one corgi, Willow, and two dorgis, Candy and Vulcan.

:: 4 - children - The Prince of Wales, the Princess Royal, the Duke of York and the Earl of Wessex.

:: 8 - grandchildren - Peter Phillips and Zara Tindall, the Duke of Cambridge and Prince Harry, Princesses Beatrice and Eugenie, and Lady Louise Mountbatten-Windsor and Viscount Severn

:: 5 - great grandchildren - Isla and Savannah Phillips, Prince George and Princess Charlotte, and Mia Tindall.

:: 13 - prime ministers in office since the start of her reign. The first was Winston Churchill (1951-55).

:: 16 - number of countries of which she is monarch - the UK and 15 Commonwealth realms.

:: 16 - general elections during the Queen's reign so far. The upcoming June 8 vote will be the 17th since she acceded to the throne.

:: 21 - age when she married the Duke of Edinburgh in November 1947.

:: 23 - number of waxworks Madame Tussauds has created of the Queen.

:: 22 - age when Princess Elizabeth had her first child, Prince Charles

:: 25 - age when she became Queen on February 6 1952.

:: 37 - age when the Queen had her last child, Prince Edward, in 1964

:: 65 - years on the throne so far. The Queen reached her Sapphire Jubilee in February 2017.

:: 70 - years of marriage the Queen and Duke of Edinburgh are due to celebrate this November - their platinum wedding anniversary.

:: 72% - proportion of her life that Elizabeth II has been Queen.

:: 601 - charities, organisations and military regiments of which the Queen is patron. She handed over 25 patronages last year.

:: 660 - investitures - the Queen has personally held more than 660 investitures since the start of her reign.

:: 23,816 - days on the throne on April 21 2017.

:: 1.45 million - approximate number of people who have attended a garden party at Buckingham Palace or the Palace of Holyroodhouse since 1952.

:: £1,771,441 - the Queen's earnings from race horse wins since 2013 in GB flat races.

:: More than 3.75 million - items of correspondence the Queen has received during her reign.

:: £340 million - the Queen's wealth, according to The Sunday Times' Rich List.