169

169 is a natural number that follows 168 and precedes 170. It is a composite number and the square of 13, with prime factorization 13^2. Its positive divisors are 1, 13 and 169.

In decimal notation it is written as 169. Its representations in other bases include binary 10101001, octal 251, and hexadecimal A9. In Roman numerals it is CLXIX.

As a square, 169 is 13^2. It is the sum of two squares, since 5^2 + 12^2 = 13^2 = 169, which highlights its connection to the famous 5-12-13 right triangle. It is also the area of a square with side length 13.

In computing and encoding contexts, decimal 169 corresponds to the Unicode code point U+00A9, which renders as the copyright symbol ©. The same value can be produced in HTML or other encodings via the numeric character reference ©.

Historically, 169 has been used as a year designation in the Gregorian and other chronologies, such as the year AD 169 in the Roman era, and similarly in years before common era. As a mathematical object, its primary significance stems from being a square of a prime and a simple example of a sum-of-squares identity.