Overview
Sixteen, written 16, is the natural number following 15 and preceding 17. It is an even integer with a long presence in counting systems, measurement units and cultural conventions. For a basic numeric reference see 16.
Mathematical characteristics
In elementary number theory, 16 has several simple but noteworthy properties. It is both a perfect square and a power of two, which makes it appear frequently in algebra and combinatorics.
- Even number: divisible by 2 and by powers of 2; see even numbers.
- Prime factorization: 2⁴ (two to the fourth power).
- Divisors: 1, 2, 4, 8, 16. The sum of proper divisors is 15, so 16 is a deficient number.
- It is the fourth square number (4²); further background: square numbers.
Representations and notation
Sixteen has simple forms across numeral systems and notations. In binary it is 10000, in octal 20 and in hexadecimal it is written as 10. In Roman numerals the conventional form for sixteen is XVI.
History, language and etymology
The English word "sixteen" combines "six" with the suffix "-teen" (an old Germanic pattern meaning ten added to a base). Historically, powers of two such as 16 were important for counting and dividing objects into equal parts, and they entered measurements and toolmaking as societies standardized units.
Common uses and cultural notes
Sixteen appears in many everyday contexts: there are 16 ounces in an avoirdupois pound; a chess player begins with 16 pieces; in music a sixteenth note subdivides the beat into four parts; and in computing, 16-bit architectures and 16 hexadecimal symbols (0–F) have been influential.
Notable distinctions
Because it is both a perfect square and a fourth power of a prime (2⁴), 16 is the smallest integer with exactly five positive divisors. Its simplicity in binary and power-of-two status make it a recurring convenience in algorithms, data representation and digital memory alignment.