If a natural number has exactly 18 divisors, then how many divisors it has at most is 3.
一个自然数恰好有18个约数，那么它最多有多少个约数的个位是3．
<gadget id="calculator">2 + 1</gadget>
<output>3</output>

<gadget id="calculator">3 * 3</gadget>
<output>9</output>

<result>9</result>