33 is the natural number following 32 and preceding 34.

Cardinal	thirty-three
Ordinal	33rd (thirty-third)
Factorization
Roman numeral	XXXIII
Binary	100001
Hexadecimal	21

In mathematics

33 is the smallest integer that can not be expressed as a sum of different triangular numbers. It is also the smallest odd repdigit that's not prime (unless we consider 1-digit integers to also be repdigits).

In science

• The atomic number of arsenic

In astronomy,

Messier object M33, a magnitude 7.0 galaxy in the constellation Triangulum, also known as the Triangulum Galaxy.

The New General Catalogue object NGC 33 , a double star in the constellation Pisces

The Saros number of the solar eclipse series which began on -1982 August 2 and ended on -485 January 17. The duration of Saros series 33 was 1496.5 years, and it contained 84 solar eclipses.

The Saros number of the lunar eclipse series which began on -1662 May 22 and ended on -364 July 10. The duration of Saros series 33 was 1298.1 years, and it contained 73 lunar eclipses.

In other fields

Thirty-three is also:

• In reference to gramophone records, 33 refers to a type of record by its revolution speed of 33⅓ revolutions per minute. 33s are also known as long playing records, or LPs. See: 78 and 45.
• A highly significant number to the Freemasons, and is one of their sacred numbers, recurring profusely throughout their 'Dogma' (as Albert Pike calls it), rituals and other miscellaneous places.
• Many people claim that they see, witness, or experience the number 33 in unusual circumstances or at a frequency that defies statistical likelihood. A popular website [1] dedicated to this repdigit, and such experiences of it, hosts comments by many such people, as well as other related resources.
• A significant number in modern numerology, as it is one of the master numbers along with 11 and 22.
• A song by the Smashing Pumpkins on their Mellon Collie and the Infinite Sadness album.
• In Spanish, the "smile to the camera" word, as is "cheese" in English. Diga treinta y tres, is the same as "say cheese".
• The code for international direct dial phone calls to France.
• Historical years: 33 A.D., 33 B.C., or 1933
• A normal human spine has 33 vertebrae where the bones that form the coccyx are counted individually.
• The great Patrick Roy of the Colorado Avalanche had the jersey #33, retired by the team in 2003