43 (forty-three) is the natural number following 42 and preceding 44.

In mathematics

Forty-three is the 14th smallest prime number. The previous is forty-one, with which it comprises a twin prime, the next is forty-seven. 43 is the smallest prime that is not a Chen prime. It is also the third Wagstaff prime.

43 is the fourth term of Sylvester's sequence.

43 is a centered heptagonal number.

Let a(0) = a(1) = 1, and thenceforth a(n) = (a(0)² + a(1)² + ... + a(n-1)²) / (n-1). This sequence continues 1 1 2 3 5 10 28 154... . Amazingly, a(43) is the first term of this sequence that is not an integer.

43 is a Heegner number.

43 is a repdigit in base 6 (111).

43 is the largest natural number that is not an (original) McNugget number.

In science

• The chemical element with the atomic number 43 (technetium) is the element with the lowest ordinal number, which does not possess stable isotopes. The technetium preceding element 42 (molybdenum) and the technetium following element 44 (ruthenium) have stable isotopes.

Astronomy

• Messier object M43, a magnitude 7.0 H II region in the constellation of Orion, a part of the Orion Nebula, and also sometimes known as de Mairan's Nebula

• The New General Catalogue object NGC 43, a barred spiral galaxy in the constellation Andromeda

• The Saros number of the solar eclipse series which began on April 29, 1513 BC and ended on June 5, 233 BC . The duration of Saros series 43 was 1280.1 years, and it contained 72 solar eclipses.

• The Saros number of the lunar eclipse series which began on August 27, 1482 BC and ended on March 15, 70. The duration of Saros series 43 was 1550.5 years, and it contained 87 lunar eclipses.

In other fields

Forty-three is also:

• The designation of Interstate 43, a freeway in Wisconsin.
• The code for direct dial international phone calls to Austria.
• Part of the title of the historical British comedy show Hancock's Forty-Three Minutes, starring Tony Hancock.
• The number of poppadoms ordered by the nine guests at a curry restaurant in Rowan Atkinson's classic Indian Waiter stand-up comedy sketch.
• Part of the title of a historical short story by Hershel Finman titled Forty-Three Rubles, about Rabbi Zvi Elimelech Spira.
• The year AD 43, 43 BC, and 1943.
• The number for Richard Petty's NASCAR racecar when he won his 7 Winston Cup Championships. He also won 200 races in his career, 95% of them in the famous #43.
• The number of distinct types of cheese requested in Monty Python's Cheese Shop sketch.
• George H. W. Bush's nickname for his son George W. Bush, the 43rd President of the United States.
• The number of enemies Gimli the Dwarf kills at the Battle of the Hornburg in The Lord of the Rings film trilogy. It was changed from the 42 originally stated in The Lord of the Rings book.
• The number of countries that Madonna's song Hung Up peaked at number 1 in.

External links

• 43folders.com, a personal blog dedicated to lifehacks, where 43 is the number of file folders required to maintain a "tickler file" in David Allen's Getting Things Done personal productivity methodology
• 43things.com, 43people.com and 43places.com, all social networking sites run by The Robot Co-op.
• interstate forty-three, a personal blog dedicated to bizarre facts about the number 43.

Integers

Cuarenta y tres | Kvardek tri | 43 (nombre) | 43 | 43 | Quarantatré | 43 (skaičius) | 43 (getal) | 43 | Quarantatrè | 43 (tall) | Quarenta e três | 43 (число) | 43 (število) | 43 (luku) | 43 (tal) | 43 | 43