Sum all the divisors of a number in pairs. Among all the sums, if the smallest is 4 and the largest is 180, what is the number?
将一个数的所有的约数两两求和，在所有的和中，若最小的是4，最大的是180，则这个数是多少．
<gadget id="calculator">3 / 1</gadget>
<output>3</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 + (1/3)</gadget>
<output>4/3 = around 1.333333</output>

<gadget id="calculator">180 / (4/3)</gadget>
<output>135</output>

<result>135</result>