math question

you can build this up from the left

one such number is

123654321

$${\frac{{\mathtt{123\,654\,321}}}{{\mathtt{9}}}} = {\mathtt{13\,739\,369}}$$

$${\frac{{\mathtt{12\,365\,432}}}{{\mathtt{8}}}} = {\mathtt{1\,545\,679}}$$

$${\frac{{\mathtt{1\,236\,543}}}{{\mathtt{7}}}} = {\mathtt{176\,649}}$$

$${\frac{{\mathtt{123\,654}}}{{\mathtt{6}}}} = {\mathtt{20\,609}}$$

$${\frac{{\mathtt{12\,365}}}{{\mathtt{5}}}} = {\mathtt{2\,473}}$$

$${\frac{{\mathtt{1\,236}}}{{\mathtt{4}}}} = {\mathtt{309}}$$

$${\frac{{\mathtt{123}}}{{\mathtt{3}}}} = {\mathtt{41}}$$

$${\frac{{\mathtt{12}}}{{\mathtt{2}}}} = {\mathtt{6}}$$

$${\frac{{\mathtt{1}}}{{\mathtt{1}}}} = {\mathtt{1}}$$

if you just work this backwards you can see how it's constructed.  Just make sure your condition is met each time you add a new digit.