41 (forty-one) is the natural number following 40 and preceding 42.

Cardinal	41 forty-one
Ordinal	41st forty-first
Factorization	prime
Roman numeral	XLI
Binary	101001
Hexadecimal	29

In mathematics

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Forty-one is the 13th smallest prime number. The next is forty-three, with which it comprises a twin prime. Forty-one is also a Sophie Germain prime and a Newman-Shanks-Williams prime. 41 is the smallest Sophie Germain prime to start a Cunningham chain of the first kind of three terms, {41, 83, 167}. It is an Eisenstein prime with no imaginary part and real part of the form $3n\; -\; 1$.

The number figures in the polynomial f(n) = n² + n + 41, which yields primes for 0 ≤ n < 40.

Forty-one is the sum of two squares, 4² + 5², as well as the sum of the first six prime numbers, and also the sum of three primes (11 + 13 + 17). Adding up the sums of divisors for 1 through 7 yields 41.

It is a centered square number.

In science

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• The atomic number of niobium.

Astronomy

• Messier object M41, a magnitude 5.0 open cluster in the constellation Canis Major
• The New General Catalogue object NGC 41, a spiral galaxy in the constellation Pegasus
• The Saros number of the solar eclipse series which began on -1588 May 28 and ended on -308 July 5. The duration of Saros series 41 was 1280.1 years, and it contained 72 solar eclipses.
• The Saros number of the lunar eclipse series which began on -1268 March 18 and ended on 30 May 6. The duration of Saros series 41 was 1298.1 years, and it contained 73 lunar eclipses.

In sports

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• Dirk Nowitzki has a jersey number of 41.

In other fields

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Forty-one is also:

• the model number of the HP-41C/CV/CX
• a number 'encoded' in a lot of the music of Johann Sebastian Bach. Bach may have considered this number a sort of signature, since given A = 1, B = 2, C = 3, etc., then B + A + C + H = 14 and J + S + B + A + C + H = 41.
• the number of the last symphony of Wolfgang Amadeus Mozart (note, however, '37' is not in the canon)
• the international direct dialling (IDD) code for Switzerland.
• Charlton Heston's designation as a galley slave in the film Ben-Hur.
• the since-retired number of the back of the uniform worn by Hall of Famers Eddie Mathews of the Braves, and Tom Seaver of the Mets
• "#41" is a song by Dave Matthews Band.
• The band Sum 41.
• C-41 process is the film developing process for 35mm color negative film.
• The year A.D. 41, 41 BC, or 1941.
• The code number given to Tetsuo Shima by scientists in the manga and 1988 film Akira
• The number that appears on Trini Alvarado's forehead in Peter Jackson's The Frighteners.
• Jonathan Pryce's destination level for his apartment in Terry Gilliam's Brazil.
• Billy Cole's jersey number in the Tony Scott film The Last Boy Scout.
• George W. Bush's nickname for his father, George H. W. Bush, the 41st President of the United States.

Integers

Cuarenta y uno | Kvardek unu | 41 (nombre) | 41 | 41 | Quarantuno | 41 (מספר) | 41 (skaičius) | 41 (getal) | 41 | Quarantùno | 41 (tall) | Quarenta e um | 41 (число) | 41 (število) | 41 (tal) | 41 | 41