We introduce a new arithmetic function $a(n)$ defined to be the number of random multiplications by residues modulo $n$ before the running product is congruent to zero modulo $n$. We give several formulas for computing the values of this function and analyze its asymptotic behavior. We find that it is closely related to $P_{1}(n)$, the largest prime divisor of $n$. In particular, $a(n)$ and $P_{1}(n)$ have the same average order asymptotically. Furthermore, the difference between the functions $a(n)$ and $P_{1}(n)$ is $o(1)$ as $n$ tends to infinity on a set with density approximately $0.623$. On the other hand, however, we see that (except on a set of density zero) the difference between $a(n)$ and $P_{1}(n)$ tends to infinity on the integers outside this set. Finally, we consider the asymptotic behavior of the difference between these two functions and find that $\sum _{n\leqslant x}(a(n)-P_{1}(n))\sim (1-\unicode[STIX]{x1D70B}/4)\sum _{n\leqslant x}P_{2}(n)$, where $P_{2}(n)$ is the second largest divisor of $n$.