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← 42 44 → 43
	← 40 41 42 43 44 45 46 47 48 49 → List of numbers — Integers 0 10 20 30 40 50 60 70 80 90 →
Cardinal	forty-three
Ordinal	43rd; (forty-third)
Factorization	prime
Divisors	1, 43
Roman numeral	XLIII
Binary	1010112
Octal	538
Duodecimal	3712
Hexadecimal	2B16

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

[edit] In mathematics

Forty-three is the 14th smallest prime number. The previous is forty-one, with which it comprises a twin prime, and 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, one more than the product of the previous terms (2 × 3 × 7).

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... (sequence A003504 in OEIS). 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.

This is the smallest number, which draws up as sum of 2,3,4,5 different primes: 43=41+2 43=11+13+19 43=2+11+13+17 43=3+5+7+11+17. The following date magic square illustrates the magic constant as the sum of four primes:

4	15	17	07
5	19	13	6
20	9	2	12
14	0	11	18

When taking the first six terms of the Taylor series for computing e, one obtains

$\sum_{i=0}^{5}\frac{1}{i!}=\frac{163}{60}=2+\frac{43}{60},\$

which is also five minus the fifth harmonic number.

43 is also 42 + 1, 4+3 = 7, 40 +3, 6x7 + 1, 13+ 3x10, 7^2 -6, 3x7+13=34 + 3^2, 13x3 +6, and 3^3 + 2^4. These attributes are perhaps coincidental.

[edit] In science

The chemical element with the atomic number 43 is technetium. It has the lowest atomic number of any element that does not possess stable isotopes.

[edit] 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.

[edit] In sports

In professional sports in the United States, the jersey number 43 has been retired for Jim Norton of Tennessee (NFL) and Dennis Eckersley of the Oakland Athletics.

In NASCAR:

The number for Richard Petty's race car when he won his 7 Winston Cup Championships. He also won 200 races in his career, 95% of them in the famous #43.
The maximum number of cars participating in a NASCAR race.

[edit] In other fields

Forty-three is:

The designation of Interstate 43, a freeway in Wisconsin.
The code for direct dial international phone calls to Austria.
The album The Dark Side of the Moon by Pink Floyd is exactly 43 minutes long.
"43", a song by Level 42 on the album Level 42
George W. Bush, 43rd president of the United States
U.S.S. Coral Sea CV-43 (Aircraft Carrier)
The name of a popular Spanish liqueur, Cuarenta y tres which is distilled with 43 different herbs and spices

[edit] Historical years

43 A.D., 43 B.C., 1943, 2043, etc.

[edit] References

Lehmer, Derrick, List of prime numbers from 1 to 10,006,721, Carnegie Institution of Washington, 1914
Wells, David, Prime Numbers: The Most Mysterious Figures in Math, Wiley, 2005, ISBN 0471462349
Crandall, Richard and Pomerance, Carl, Prime Numbers: A Computational Perspective, Springer, 2005, ISBN 0387252827

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