38. The combat power of Beidou Xing Si and Nan Xizi are both three-digit numbers $\overline{a b c}$. When the Ultra Ring lights up, the two merge to transform into an Ultra Man, and the transformed Ultra Man's combat power rises to a six-digit number $\overline{d e f a b c}$, and $\overline{d e f a b c}=\overline{a b c} \times \overline{a b c}$, where the same letters represent the same digits, and different letters represent different digits. Therefore, the six-digit number $\overline{d e f a b c}=$ $\qquad$
$390625$