[yahelc]

223.

EDIT: 219 is definitely smaller than 223.

[burgerbrain]

219

Edit: on the other hand, in the math category "219 is the smallest number that can be represented as a sum of four positive cubes in two different ways."

[michaelochurch]

223 is a US date-prime. 2 and 23 is prime, and so is 223.

That may be a stretch, but it qualifies as something interesting.