\[2640 = 2 \bullet 1320 = 2 \bullet 2 \bullet 660 =\]
\[= 2 \bullet 2 \bullet 2 \bullet 330 =\]
\[= 2 \bullet 2 \bullet 2 \bullet 2 \bullet 165 =\]
\[= 2 \bullet 2 \bullet 2 \bullet 2 \bullet 3 \bullet 55 =\]
\[= 2 \bullet 2 \bullet 2 \bullet 2 \bullet 3 \bullet 5 \bullet 11 =\]
\[= 2^{4} \cdot 3 \cdot 5 \cdot 11\]