A little bit of calculation will suffice!

For some positive integers $A,B,C$ and $D$ , the following equation is true.

$\text{If }\mathbf{A}\text{ takes the maximum possible value, find out the product of seven leftmost digits of }\mathbf{A}.$

$\boxed{\text{For example, if }\mathbf{A=123456789}\text{ then your answer will be }\mathbf{1\times2\times3\times4\times5\times6\times7 = 5040}}$