Thursday, February 26, 2009

219

219 = 3 x 73.

219 is the smallest number with two representations as a sum of four positive cubes: 219 = 13 + 13 + 13 + 63 = 33 + 43 + 43 + 43.

The number
219n + 2 is prime for the smallest three primes (2, 3, 5): 2192 + 2 = 47963, 2193 + 2 = 10503461, 2195 + 2 = 503756397101.

219 is 11011011 in base 2 (binary) and 333 in base 8.

219 is the number of space groups in three dimensions, analogous to the 17 basic wallpaper patterns in two dimensions, without considering handedness. When including handed forms, they determine the possible shapes of mineral crystals.

Source:
The Penguin Dictionary of Curious and Interesting Numbers, rev. ed., by David Wells.
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