Question

For g ∈ $\Z$, let $\bar{g}$ ∈ $\Z_8$ denote the residue class of g modulo 8. Consider the group $\Z^×_8$ = {$\bar{x}$ ∈ $\Z_8$ : 1 ≤ x ≤ 7, gcd(x, 8) = 1} with respect to multiplication modulo 8. The number of group isomorphisms from $\Z^×_8$ onto itself is equal to ________

Answer 1

The correct answer is 6.