215 (number)

215 (two hundred [and] fifteen) is the natural number following 214 and preceding 216.

In mathematics

 * 215 is a composite number and a semiprime ($$=5\times43$$).
 * $$215 = (3!)^3 - 1$$.
 * 215 is the second smallest integer (after 5) such that $$n^2-17$$ is twice a square: $$215^2-17 = 2 \times 152^2$$.
 * 215 is a vertically symmetric number on a calculator display.
 * There are 215 sequences of four integers, counting re-arrangements as distinct, such that the sum of their reciprocals is 1. These are:
 * 24 arrangements of (2,3,7,42), (2,3,8,24), (2,3,9,18), (2,3,10,15), (2,4,5,20) and (2,4,6,12).
 * 12 arrangements of (3,3,4,12), (3,4,4,6), (2,3,12,12), (2,4,8,8) and (2,5,5,10).
 * 6 arrangements of (3,3,6,6).
 * 4 arrangements of (2,6,6,6).
 * 1 arrangement of (4,4,4,4).

In other fields

 * 215 Oenone is a main belt asteroid.
 * E215 is the E number of Sodium ethyl para-hydroxybenzoate.
 * There are several highways numbered 215.

215 is also:
 * The Dewey Decimal Classification for Science and religion.
 * The year AD 215 or 215 BC
 * 215 is often used as slang for marijuana, from California Proposition 215, legalizing it for medical use.
 * The first area code of metropolitan Philadelphia, Pennsylvania