\[\boxed{\mathbf{2.}\mathbf{39}}\]
Пояснение.
Решение.
\[\mathbf{Простые\ делители\ чисел:}\]
\[A(64) = \left\{ 2 \right\};\]
\[A(72) = \left\{ 2;3 \right\};\]
\[A(221) = \left\{ 13;17 \right\};\]
\[A(247) = \left\{ 13;19 \right\};\]
\[A(7777) = \left\{ 7;11;101 \right\};\]
\[A(7007) = \left\{ 7;11;13 \right\}.\]