172 (number)
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172 is a natural number that follows 171 and precedes 173. It is an even number, meaning it is divisible by two with no remainder. It is also a composite number, as it has divisors other than one and itself.
In the decimal system, 172 comprises three digits: 1, 7, and 2. The sum of these digits is 1+7+2 = 10. Therefore, 172 is not divisible by three, since the sum of its digits is not divisible by three.
Mathematical properties
The prime factorization of 172 is 2² × 43. Its divisors are 1, 2, 4, 43, 86, and 172—six divisors in total. The sum of all its divisors is 308, while the sum of its proper divisors (those excluding the number itself) is 136. Since 136 is less than 172, the number is classified as deficient.
In binary, 172 is written as 10101100. In hexadecimal, it is AC. In Roman numerals, it is written CLXXII. 172 is not a perfect square, as 13² = 169 and 14² = 196 are its nearest neighbors.
Relationship to other numbers
172 is the square of 2 multiplied by 43, which is a prime number. Therefore, 172 is of the form 4p, with a divisor structure determined only by 2 and 43. It is also possible to express it as a sum of consecutive integers in abbreviated forms, though these various representations depend on the rules of sequence summation.
Common usage
Like other three-digit numbers, 172 is used as a label or identifier for road numbers, historical years, measurements, and various codes. Such usage reflects no mathematical property of the number itself, but rather serves as a way to distinguish different things.