41 is the natural number following 40 and preceding 42.

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}.

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). It is a centered square number.

In 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 other fields

Forty-one is also:

• the atomic number of niobium.
• the model number of the HP-41C/CV/CX
• in A Thousand and One Nights, the number of thieves accompanying Ali Baba.
• 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 code for direct dial international phone calls to Switzerland.
• #41 is a song by Dave Matthews Band.
• C-41 is the film developing process for 35mm color negative film.
• The year A.D. 41, 41 BC, or 1941.