156 (number)
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156 is a natural number that lies between 155 and 157. It is an even number, since it is divisible by two, and a composite number—meaning it has divisors other than 1 and itself.
In decimal notation it consists of three digits. In Roman numerals it is written CLVI. In binary it is 10011100.
Mathematical properties
The prime factorization of 156 is 2² × 3 × 13. Its divisors are 1, 2, 3, 4, 6, 12, 13, 26, 39, 52, 78, and 156—a total of 12. The sum of all its divisors is 392; since its proper divisors (excluding itself) sum to 236, which exceeds 156, it is an abundant number.
156 is a pronic number, being the product of two consecutive integers: 12 × 13 = 156. Consequently it equals twice the 12th triangular number, which is 78 (156 = 2 × 78).
Additionally, 156 is divisible by the count of its divisors (12), since 156 ÷ 12 = 13. Numbers with this property are known as refactorable or tau numbers.
General use
Like other small numbers, 156 serves as a label in many contexts: road numbers, codes, historical dates (such as year 156 CE), and chapter or section numbers in books or regulations. Such usage has no actual connection to the mathematical properties listed above.