2, 3, 5, 7, 11, ... are all prime numbers, that is to say, each number is only divisored by 1 and itself. It is known that the length and width of a rectangle are both prime units, and the perimeter is 36 units. What is the maximum square unit of the area of this rectangle?
2，3，5，7，11，…都是质数，也就是说每个数只以1和它本身为约数．已知一个长方形的长和宽都是质数个单位，并且周长是36个单位．问这个长方形的面积至多是多少个平方单位？
<gadget id="calculator">7 * 11</gadget>
<output>77</output>

<result>77</result>