$4 6 1 3 4 3$ is the code for Tahiti.
Use it to find the names of the following islands:
\begin{align} 16343, \qquad 38326, \qquad 8653. \end{align}
From Tahiti we have:
$16343$: _aiti.
$38326$: I_i_a.
$8653$: _a_i.
The unknown letters are from number $1$, $2$, $5$ and $8$. It is easy to find the islands by brute-force (Haiti, Ibiza, Bali), however I cannot find any pattern in the numbers/letters. Can you?