216

216 = 2 x 2 x 2 x 3 x 3 x 3.

216 = 6³ is a perfect cube. 216 = 6^{(2 + 1)}.

216 = 21 + 20 + 19 + 18 + 17 + 16 + 15 + 14 + 13 + 12 + 11 + 10 + 9 + 8 + 7 + 6.

216 is the smallest cube that can be written as the sum of three cubes: 216 = 5³ + 4³ + 3³.

216 is the smallest number that can be expressed as the difference of the sums of the squares of successive twin primes: 216 = (13² + 11²) - (7² + 5²).

216 is 1331 in base 5.

216 is the sum of a twin prime pair: 216 = 107 + 109.

In the film Pi, Max Cohen becomes obsessed with a 216-digit number in his quest to find a numeric equation behind existence.

Source: Prime Curios! and Wikipedia