631

This number is a prime.

The tetractys (pronounced "tet-trak'tis") is a triangular figure consisting of ten vertices arranged in four rows: one, two, three, and four dots in each row. It was a mystical symbol to the Pythagoreans, who lived during the 6th century B.C. There are fifteen primes in the figure below (reading forwards or backwards along the indicated lines), the largest of which is 631.

                    (0)
                    / \
                  (1)-(2)
                  / \ / \
                (3)-(4)-(5)
                / \ / \ / \
              (6)-(7)-(8)-(9)

Can you rearrange these digits and achieve two dozen primes?