Step 1: Find the least common multiple (LCM) of the divisors.
Divisors: 15, 25, 40, 75.
LCM of 15, 25, 40, and 75 = 600
Step 2: Determine the largest four-digit number divisible by the LCM.
The largest four-digit number = 9999
\[
\text{Largest multiple} = \left\lfloor \frac{9999}{600} \right\rfloor \times 600 = 9600
\]