The quotient group $\mathbb{Z}/n\mathbb{Z}$ (integers modulo $n$) is isomorphic to $\mathbb{Z}_n$ — the cyclic group of order $n$. By the First Isomorphism Theorem, $\mathbb{Z}/\ker\phi \cong \text{Im}(\phi)$, where $\phi: \mathbb{Z}\to\mathbb{Z}_n$ is the natural surjective homomorphism $\phi(k) = k\mod n$.