20 (twenty) is the natural number following 19 and preceding 21. Twenty is a composite number, its proper divisors being 1, 2, 4, 5 and 10. It is also the sum of the first four triangular numbers, making it a tetrahedral number. Twenty is the smallest abundant number that is not a multiple of 3. It is a Harshad number and a self number.
The ordinal form is “twentieth.” Twenty is factored 2^2 * 5. Twenty is represented in Roman numerals as XX, and in binary as 10100.
It is the total number of digits on the human body, which makes it a possible candidate for a numeral system. Twenty is used as a radix for vigesimal number systems. In the old British currency system, there were twenty shillings in a pound.
A polyhedron with twenty faces is an icosahedron.
Twenty is the first number in an early Indian magic square of order 3.
In science, twenty is the atomic number of calcium, the third Magic number (physics), and the number of proteinogenic amino acids that are encoded by the standard genetic code.
In astronomy, twenty may refer to Messier object M20, a magnitude 5.0 nebula/open cluster in the constellation Sagittarius, also known as the Trifid Nebula, or New General Catalogue object NGC 20, a spiral galaxy in the constellation Andromeda.
In a game of chess both players have 20 first moves from which to choose.
The number 20 is used as an index in measuring visual acuity. 20/20 indicates normal vision at 20 feet, although it is commonly used to mean “perfect vision.” When someone is able to see only after an event how things turned out, that person is often said to have had “20/20 hindsight.”
Twenty questions is a popular party game.
Twenty is the age of majority in Japanese tradition. Someone who is exactly twenty years old is described as hatachi.
The “Twenty Year Curse” refers to the pattern of the president of the United States elected every twenty years starting with 1840 to die in office. This pattern failed when Reagan survived his time in office.
NASCAR star Tony Stewart drives a car with the number 20 on it.
Bands with the number twenty in their name include Matchbox 20.
A group of twenty units is often referred to as a score.
Furthermore, twenty can refer to the code for international direct dial phone calls to Egypt; Twenty, a village in Lincolnshire; in the United States Constitution, $20 is the threshold value of civil disputes above which the right to trial by jury is preserved; the denomination of U.S. dollar with Andrew Jackson’s portrait; the designation of Interstate 20, a freeway that runs from Texas to South Carolina; Twenty, a 1997 album by Lynyrd Skynyrd; historical years: 20 A.D., 20 B.C., or 1920; used as part of the 10-code system to reference to a person or object’s location (”What’s your twenty?”).
Oh, and twenty is now my current age.
15 August in History
1620 - The Mayflower pulled out of Southampton, England
1877 - Thomas Edison made the first-ever recording - "Mary Had a Little Lamb"
1914 - Panama Canal opens to traffic
1945 - VJ Day; Japan surrenders unconditionally, ending World War II
1947 - India gains independence from Britain
1961 - Construction begins on the Berlin Wall
1969 - First day of Woodstock Music and Art Festival
1985 - I was born
Others Born on 15 August
1769 - Napoleon Bonaparte, Emperor of France (d. 1821)
1912 - Julia Child, American cook (d. 2004)
1950 - Princess Anne of the United Kingdom
1968 - Debra Messing, actress
1972 - Ben Affleck, American actor