9. (12 points) Use the digits 1 to 9 to form a nine-digit number $\overline{B C D E F G H I}$ without repeating any digit, such that $\overline{\mathrm{AB}} 、 \overline{\mathrm{BC}} 、 \overline{\mathrm{CD}}$ 、 $\overline{\mathrm{DE}}, \overline{\mathrm{EF}} 、 \overline{\mathrm{FG}} 、 \overline{\mathrm{GH}}, \overline{\mathrm{HI}}$ these eight two-digit numbers can all be expressed as the product of two single-digit numbers; then the result of the expression $\overline{\mathrm{ABC}}+\overline{\mathrm{DEF}}+\overline{\mathrm{GHI}}$ is $\qquad$ .
【Solution】Solution: The number that can be paired with 9 is only 4. So, at the end $\overline{\mathrm{HI}}=49$. The number that can be paired with 7 is only 2, either 27 or 72, but there can only be one number, so $\overline{\mathrm{AB}}=72$. Next, analyze the number 3, the combinations can only be 63 and 35. The number 5 can only be followed by $54 . \therefore \overline{\mathrm{EF}}=35$. Next, analyze the number 8, the combinations can be $28,18,81$, so $\overline{\mathrm{BC}}=28 . \overline{\mathrm{CD}}=81$.
$$
\overline{\mathrm{ABC}}+\overline{\mathrm{DEF}}+\overline{\mathrm{GHI}}=728+163+549=1440 \text {. }
$$

Therefore, the answer is: 1440.