33 (thirty-three) is the natural number following 32 and preceding 34.

In mathematics

33 is the largest positive 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).

The sum of the first four factorials is 33. Adding up the sums of divisors for the 1 through 6 yields 33. 33 is the smallest integer such that it and the next two integers all have the same number of divisors.

In science

• The atomic number of arsenic

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 sports

• The number of innings played in the longest baseball game in history (a 1981 minor league game between the Rochester Red Wings and the Pawtucket Red Sox in Pawtucket, Rhode Island).
• Retired numbers of former basketball star Larry Bird and former baseball star Eddie Murray.
• Number of retired hockey goalie Patrick Roy.
• Jersey number of basketball player Patrick Ewing. The number was retired on February 28, 2003 in a large ceremony at Madison Square Garden.
• Name and lucky number of the Danish flag football team Odense 33

In other fields

• Jesus's age when he was crucified in 33 A.D., according to many, though not verified historically
• Alexander the Great died at the age of thirty-three
• 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 one of their sacred numbers, recurring profusely throughout their rituals
• 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 is dedicated to this digit
• The best-known car number of retired NASCAR driver Harry Gant
• A significant number in modern numerology, 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. Also a song by Coheed and Cambria on their The Second Stage Turbine Blade album (the songs are not related)
• The title of the first episode of the new Battlestar Galactica television series
• In Spanish, the "smile to the camera" word, as is "cheese" in English. Diga treinta y tres ("Say thirty-three") is the same as "Say cheese"
• In French, Italian, Romanian and Spanish, the word a patient is usually asked to say when a doctor is listening to his or her lungs with a stethoscope (Trente-Trois, Trentatrè, Treizeci şi trei, and Treinta y Tres)
• The code for international direct-dial phone calls to France
• A normal human spine has 33 vertebrae when the bones that form the coccyx are counted individually
• The number printed on all Rolling Rock beer labels
• The number of chapters per series of DarkSoul Kingdom, an online fantasy story
• Number of Cantos in each of Dante's 3 parts of the Divine Comedy
• Number of maximum European Credit Transfer and Accumulation System credits that Instituto Superior Técnico's students are allowed to achieve throughout one semester

Historical years

Integers | Famous numbers

33 (tal) | Treinta y tres | Tridek tri | 33 (nombre) | 33 | 33 | Trentatré | 33 (skaičius) | 33 (getal) | 33 | Trentatrè | 33 (tall) | 33 (liczba) | Trinta e três | 33 (число) | 33 (število) | 33 (tal) | 33 | 33