There are four different natural numbers whose sum is 1991. If the greatest common divisor of these four numbers is required to be as large as possible, what is the largest number among these four numbers?
有四个不同的自然数，它们的和是1991．如果要求这四个数的最大公约数尽可能的大，这四个数中最大的那个数是多少．
<gadget id="calculator">5 * 181</gadget>
<output>905</output>

<result>905</result>