A rectangle is surrounded by a wire with a length of 16 cm. If the length and width are prime numbers, what is its area in cm**2.
用一条长16cm的铁丝围成一个长方形，如果长和宽都是质数，它的面积是多少cm**2．
<gadget id="calculator">5 * 3</gadget>
<output>15</output>

<result>15</result>