x mod 6 | 0 | 1 | 2 | 3 | 4 | 5 | |
0 | 0 | 0 | 0 | 0 | 0 | 0 | not a zero divisor because zero doesn't count as a zero divisor |
1 | 0 | 1 | 2 | 3 | 4 | 5 | 1 is a unit because 1*1=1 |
2 | 0 | 2 | 4 | 0 | 2 | 4 | 2 is a zero divisor because 2*3=0 (and 2,3 both not zero) |
3 | 0 | 3 | 0 | 3 | 0 | 3 | 3 is a zero divisor because 3*2=0 and 3*4=0 |
4 | 0 | 4 | 2 | 0 | 4 | 2 | 4 is a zero divisor because 4*3=0 |
5 | 0 | 5 | 4 | 3 | 2 | 1 | 5 is a unit because 5*5=1 |