| z | 2 = a 2 − ab + b 2 is a natural prime (necessarily congruent to 0 or 1 mod 3). It follows that the square of the absolute value of every Eisenstein prime is a natural prime or the square of a natural prime. In base 12, the natural Eisenstein primes are exactly the natural primes ending with 5 or 3 (i.e. the natural primes congruent to 2 ...
