The number 239 is an integer that follows 238 and precedes 240. It is an odd number and can be classified as a prime number, meaning it has no positive divisors other than 1 and itself. In mathematics, prime numbers are significant because they are the building blocks of whole numbers. In the context of science, 239 is notable for its association with the isotope plutonium-239, which is used in nuclear reactors and atomic bombs. This isotope has a half-life of about 24,100 years and is a key material in the field of nuclear energy and weaponry.