Equilateral hexagons can be put together in a flower-like way:
From the picture above you can clearly see that 7 hexagons are necessary to built a "two-row"-flower. If we built a three row flower, 19 hexagons are needed.
7 and 19 are both primes. If we add more rows will we ever be able to make a hexagon-flower with a *non-prime* total amount of hexagons?