138 (number)
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138 is a natural number that comes after 137 and before 139. It is an even number, meaning it is divisible by two with no remainder. It is also a composite number, as it has factors other than one and itself.
In Roman numerals it is written CXXXVIII. In binary notation it is written 10001010, and in hexadecimal notation it is 8A.
Properties
The prime factorization of 138 is 2 × 3 × 23. All three are distinct primes, which makes 138 a sphenic number—a number that is the product of exactly three different primes.
The divisors of 138 are 1, 2, 3, 6, 23, 46, 69, and 138. The sum of its proper divisors (all divisors except the number itself) is 147, which exceeds 138. Therefore 138 is an abundant number.
138 is also equal to the sum of four consecutive primes: 29 + 31 + 37 + 41 = 138.
General usage
Like other numbers, 138 is used in notation and labeling: road numbers, year notation (such as the year 138 CE), sections of laws, and identifiers for groups or equipment. Such uses are arbitrary designations unrelated to the mathematical properties of the number.