40. Find a five-digit number that has the following property: when multiplied by 9, the result is a number composed of the same digits but in reverse order, i.e., the number is reversed.
40. Multiply the desired number by 10 and subtract the desired number from the product, which is equivalent to multiplying by 9, then $\overline{a b c d e o}-\overline{a b c d e}=\overline{e d c b a}$. It is easy to establish that $a=1$, then $e=9, b=0, d=8, c=9$. The desired number is 10989.