> Then comes 2: the first number that is divisible, but only by itself and the indivisible one. This does hold in the ring Z. In the ring Z[i], 2 = (1+i)*(1-i)

> Then comes 2: the first number that is divisible, but only by itself and the indivisible one. This does hold in the ring Z. In the ring Z[i], 2 = (1+i)*(1-i), and the two factors are prime elements.