A rectangle is surrounded by an iron wire with a length of 18cm. If the length and width are both prime numbers, what is the area of the rectangle in cm**2.
用一条长18cm的铁丝围成一个长方形，如果长和宽都是质数，这个长方形的面积是多少cm**2．
<gadget id="calculator">7 * 2</gadget>
<output>14</output>

<result>14</result>