16

16 is the natural number that follows 15 and precedes 17. In decimal notation it is written as 16. It is a composite number with prime factorization of 2^4, and it is the smallest positive integer with exactly five divisors: 1, 2, 4, 8, and 16. It is a perfect square, equal to 4^2, and it is a power of two.

Representations in other bases include binary 10000, octal 20, and hexadecimal 10; in Roman numerals it is XVI. In computing and digital electronics these alternate representations are common, with hexadecimal (base-16) widely used to encode data and memory addresses.

In science, sulfur has atomic number 16 and the symbol S; sulfur is an essential element for life and occurs in many minerals and biomolecules. In culture and history, the 16th Amendment to the United States Constitution, ratified in 1913, authorizes individual and corporate income taxation. The term sweet sixteen refers to a coming-of-age celebration in some cultures, and the 16th century covers the years 1501–1600.

In mathematics and games, 16 is notable for being both a square (4^2) and a power of two (2^4). A standard 4x4 chessboard contains 16 unit squares. In computing and digital systems, 16 features prominently as a base (hexadecimal), a common word size (16-bit), and a color depth reference (16-bit color allows 65,536 colors).