The greatest four digit number which is divisible by 15, 25, 40 and 75 is
9600
L.C.M of 15, 25, 40 and 75 is 600
Largest 4 digits number is 9999.
When 9999 is divided by 600, the remainder will be 399.
So, the required number is (9999 - 399) = 9600