216

216 is a natural number that comes after 215 and before 217. In mathematics, 216 is notable as a perfect cube since 216 = 6^3. It has the prime factorization 2^3 · 3^3, which yields 16 positive divisors. The sum of its divisors is 600, and 216 is a Harshad (Niven) number because it is divisible by the sum of its digits (2+1+6 = 9; 216 ÷ 9 = 24).

In various numeral systems, 216 has the following representations: binary 11011000_2, octal 330_8, decimal 216, hexadecimal D8_16, and in base 3 it is 22000_3, while in base 6 it is 1000_6.

In calendar and history, 216 refers to the year 216 CE/AD, a point in the late Roman Empire era. Specific events from that year are not widely summarized in general references.

In astronomy, the number 216 appears in the designation of the main-belt asteroid 216 Kleopatra, which carries the catalog number 216. The asteroid is named after Cleopatra and is noted for its distinctive shape.

The number 216 also reflects the cubic symmetry of many geometric contexts, since it is the cube of 6 and a product of small prime powers. Its properties as a cube and as a highly composite-like factorization make it a frequently cited example in number theory discussions.

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