\[\boxed{\mathbf{363}.}\]
\[Пусть\ \text{x\ }и\ y - данные\ числа.\]
\[Составим\ систему\ уравнений:\]
\[\left\{ \begin{matrix} xy = 135\ \\ x - y = 6 \\ \end{matrix} \right.\ \text{\ \ \ \ \ \ \ }\left\{ \begin{matrix} x = 6 + y\ \ \ \ \ \ \ \ \ \ \ \\ (6 + y)y = 135 \\ \end{matrix} \right.\ \]
\[y^{2} + 6y - 135 = 0\]
\[D_{1} = 9 + 135 = 144\]
\[y_{1} = - 3 + 12 = 9;\ \ \ \]
\[y_{2} = - 3 - 12 = - 15;\]
\[x_{1} = 6 + 9 = 15;\ \ \ \ \ \ \ \]
\[x_{2} = 6 - 15 = - 9.\]
\[Ответ:( - 9; - 15)\ или\ (15;9).\]