Is every sufficiently large even integer the sum of (any number of) distinct primes?
No doubt this question has been asked before; does the conjecture/theorem have a name? It is related to Goldbach's conjecture, which states that every even integer is the sum of two (not necessarily distinct) primes.
The even integer $6$ can not be expressed as a sum of distinct primes as its only prime representations are $2+2+2$ and $3+3$, thus the condition "sufficiently large" is necessary. If the condition "distinct" is removed, the statement becomes obvious ($n$ copies of $2$).