82 (number)

82 is a natural number that follows 81 and precedes 83. It is an even number, since it is divisible by 2 with no remainder. It is also a composite number, meaning it has divisors other than 1 and itself.

In standard base-10 notation, 82 consists of two digits: 8 in the tens place and 2 in the ones place. In base 2 (binary), it can be written as 1010010.

Mathematical properties

82 equals 2 × 41. Both of these factors are prime numbers, so 82 belongs to the class known as semiprimes—numbers that are the product of exactly two prime numbers. Its divisors are 1, 2, 41, and 82; their sum is 126, while the sum of its proper divisors (excluding 82 itself) is 44. Since 44 is less than 82, it is a deficient number.

82 can be expressed as the sum of two squares: 82 = 81 + 1 = 9² + 1². It therefore belongs to the class of numbers expressible as sums of two squares. Applying the iterative process of summing the squares of digits—8² + 2² = 68, then 6² + 8² = 100, then 1—it terminates at 1. By this mathematical definition, 82 is a happy number.

Use and designation

In chemistry, 82 is the atomic number of lead (Pb). In the international telephone numbering plan, +82 is the country code for South Korea. Designations of this type represent agreed-upon conventions rather than intrinsic mathematical properties of the number.