72

72 is an integer that follows 71 and precedes 73. In decimal it is written as 72; in Roman numerals it is LXXII; in binary as 1001000; in octal as 110; and in hexadecimal as 0x48. The ASCII code 72 corresponds to the uppercase letter H, and in Unicode the code point U+0048 denotes the same character.

In mathematics, 72 factors as 2^3 × 3^2. It has twelve positive divisors: 1, 2, 3, 4, 6, 8, 9, 12, 18, 24, 36, and 72. The sum of its divisors is 195, so the sum of proper divisors is 123, which makes 72 an abundant number. It is a composite number, not prime and not a perfect square. Its prime factorization underpins its multiple divisors and its role in base representations and divisor-related properties.

In science, 72 is the atomic number of hafnium (symbol Hf), a transition metal used in various alloys and, historically, in nuclear applications such as certain types of reactor control rods due to its neutron-related properties. The name hafnium derives from Hafnia, the Latin name for Copenhagen.

In geometry and culture, 72 appears in several contexts. The central angle between adjacent vertices of a regular pentagon is 72 degrees, as is the exterior angle of a regular pentagon. In cultural traditions, the number 72 is notable for the “72 Names of God” in Kabbalah, a set of names derived from biblical verses; and it is also used to denote a three-day period (72 hours).