A good hash function satisfies (approximately) the assumption of simple uniform hashing : each key is equally likely to hash to any of the $m$ slots, independently of where any other key has hashed to.
Coming to the Hash function, $h(k) = k \,\,mod(m)$, we usually avoid certain values of $m$. For example, $m$ should not be a power of $2$, since if $m$ = $2^p$, then $h(k)$ is just the $p$ lowest-order bits of $k$. Unless we know that all low-order $p-bit$ patterns are equally likely, we are better off designing the hash function to depend on all the bits of the key.
A prime not too close to an exact power of 2 is often a good choice for $m$.
We could choose $m = 701$ because it is a prime and not near any power of 2.
$81$ Not a Prime. $61$ is near $2^6$
