48

This number is a composite.

The smallest possible sum for a set of four distinct primes such that the sum of any three is prime: {5, 7, 17, 19}.

Questions: Is there a prime quadruplet (of the form {p, p+2, p+6, p+8}) with this property? (Click here for answer.) How about prime sextuplets, where the sum of any five are prime? (Click here for answer.) Or greater admissible prime constellations (k-tuples) such that the sum of any k-1 primes is prime? Update: Jens Kruse Andersen has found that due to divisibility by small primes, there is no k from 7 to 50 for which there exists a prime k-tuplet such that the sum of any k-1 is prime.