239 (two hundred [and] thirty-nine) is the natural number following 238 and preceding 240. In mathematics, a natural number is either a positive integer (1, 2, 3, 4, ...) or a non-negative integer (0, 1, 2, 3, 4, ...). The former definition is generally used in number theory, while the latter is preferred in set theory. ...

In linguistics, cardinal numbers is the name given to number words that are used for quantity (one, two, three), as opposed to ordinal numbers, words that are used for order (first, second, third). ... Commonly, ordinal numbers, or ordinals for short, are numbers used to denote the position in an ordered sequence: first, second, third, fourth, etc. ... In mathematics, factorization or factoring is the decomposition of an object (for example, a number, a polynomial, or a matrix) into a product of other objects, or factors, which when multiplied together give the original. ... In mathematics, a prime number (or prime) is a natural number greater than one whose only positive divisors are one and itself. ... The system of Roman numerals is a numeral system originating in ancient Rome, and was adapted from Etruscan numerals. ... The binary numeral system represents numeric values using two symbols, typically 0 and 1. ... In mathematics and computer science, hexadecimal, or simply hex, is a numeral system with a radix or base of 16 usually written using the symbols 0–9 and A–F or a–f. ...

In mathematics

It is a prime number. The next is 241, with which it comprises a pair of twin primes. 239 is a Sophie Germain prime and a Newman-Shanks-Williams prime. It is an Eisenstein prime with no imaginary part and real part of the form 3n − 1. Because the next odd number, 241 is prime, 239 is a Chen prime. In mathematics, a prime number (or prime) is a natural number greater than one whose only positive divisors are one and itself. ... A twin prime is a prime number that differs from another prime number by two. ... A prime number p is called a Sophie Germain prime if 2p + 1 is also prime. ... This can be abbreviated to NSW, which is also the abbreviation of the state of New South Wales in Australia. ... An Eisenstein prime is an Eisenstein integer aω + b that has only two Eisenstein divisors, the complex cube root of unity and aω + b itself. ... A prime number p is called a Chen prime if p + 2 is either a prime or a semiprime. ...

HAKMEM (incidentally AI memo 239 of the MIT AI Lab) included an item on the properties of 239, including these: HAKMEM, alternatively known as AI Memo 239, is a 1972 memo (technical report) of the MIT AI Lab that describes a wide variety of hacks, primarily useful and clever algorithms for mathematical computation. ... ...

• When expressing 239 as a sum of square numbers, 4 squares are required, which is the maximum that any integer can require; it also needs the maximum number (9) of positive cubes (23 is the only other such integer), and the maximum number (19) of fourth powers.
• 239/(13)² is a convergent to the continued fraction of the square root of 2, so that 239² = 2 · 13⁴ - 1.
• Related to the above, π/4 = 4 arctan(1/5) - arctan(1/239).
• 239 · 4649 = 1111111, so 1/239 = 0.0041841 repeating, with period 7.
• 239 can be written as bⁿ - b^m - 1 for b = 2, 3, and 4, a fact evidenced by its binary representation 11101111, ternary representation 22212, and quaternary representation 3233.

In square numbers, a square number, sometimes also called a perfect square, is an integer that can be written as the square of some other integer. ... In arithmetic and algebra, the cube of a number n is its third power — the result of multiplying it by itself two times: n3 = n × n × n. ... For a discussion of convergence and convergent series, see limit (mathematics). ... In mathematics, a continued fraction is an expression such as where a0 is some integer and all the other numbers an are positive integers. ... The square root of 2 is equal to the length of the hypotenuse of a right triangle with legs of length 1. ... Lower-case pi The mathematical constant Ï€ is a real number which may be defined as the ratio of a circles circumference (Greek περιφέρεια, periphery) to its diameter in Euclidean geometry, and which is in common use in mathematics, physics, and engineering. ... The binary numeral system represents numeric values using two symbols, typically 0 and 1. ... Ternary is the base-3 numeral system. ... Quaternary is the base four numeral system. ...

In other fields

239 is also:

• K239 is Mozart's only work for two orchestras.
• In The Simpsons episode "Homer's Night Out", Homer weighs himself and resolves to exercise. Six months later he weighs himself again and again resolves to exercise. Both times he weighed exactly 239 pounds.
• The years A.D. 239 and 239 BC.