53 is the natural number following 52 and preceding 54.

In mathematics

Fifty-three is the 16th smallest prime number. The next is fifty-nine. Fifty-three is also a Sophie Germain prime, and the sum of five consecutive primes (5 + 7 + 11 + 13 + 17). But 53 can not be expressed as the sum of any integer and its base 10 digits, making 53 a self number.

53 written in hexadecimal is 35, that is, the same characters used in the decimal representation, but reversed. Three multiples of 53 share this property: 371 = 173₁₆, 5141 = 1415₁₆, 99481 = 14899₁₆.

53 is a strictly non-palindromic number, it is not palindromic in any base from base 2 to base 51.

In science

• The atomic number of iodine

In astronomy,

Messier object M53, a magnitude 8.5 globular cluster in the constellation Coma Berenices

The New General Catalogue object NGC 53 , a magnitude 12.6 barred spiral galaxy in the constellation Tucana

The Saros number of the solar eclipse series which began on -1295 August 26 and ended on 220 February 21. The duration of Saros series 53 was 1514.5 years, and it contained 85 solar eclipses.

The Saros number of the lunar eclipse series which began on -993 June 5 and ended on 287 July 12. The duration of Saros series 53 was 1280.1 years, and it contained 72 lunar eclipses.

In other fields

Fifty-three is also:

• The code for international direct dial phone calls to Cuba.
• In the title of the 1912 movie North of Fifty Three, remade in 1917.
• The number of short poems in the book Rumi Birdsong by Jelaluddin Rumi .
• The year AD 53, 53 BC, and 1953.