6. (5 points) There is a natural number, the difference between its smallest two divisors is 4, and the difference between its largest two divisors is 308, then this natural number is $\qquad$
【Solution】Solution: Since the smallest divisor is 1, the second smallest divisor is $1+4$, so the largest divisor is itself $x$, and the second largest divisor is $x \div 5$,

Therefore, $x-x \div 5=308$,
$$
\begin{aligned}
x-\frac{x}{5} & =308, \\
\frac{4}{5} x & =308, \\
x & =308 \div \frac{4}{5}, \\
x & =308 \times \frac{5}{4}, \\
x & =385 ;
\end{aligned}
$$

The answer is: 385 .