\[\boxed{\mathbf{3.422}}\]
Пояснение.
Решение.
\[420 \rightarrow 4 + 2 + 0 = 6\]
\[422 \rightarrow 4 + 2 + 2 = 8\]
\[424 \rightarrow 4 + 2 + 4 = 10\]
\[426 \rightarrow 4 + 2 + 6 = 12\]
\[428 \rightarrow 4 + 2 + 8 = 14\]
\[430 \rightarrow 4 + 3 + 0 = 7\]
\[432 \rightarrow 4 + 3 + 2 = 9\]
\[Делятся\ на\ 3:\ \ \]
\[420;426;\ \ 432.\]
\[Кратны\ 9:\ \ \]
\[432.\]