The CAS Registry Mumber 6596-74-3 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 6,5,9 and 6 respectively; the second part has 2 digits, 7 and 4 respectively. Calculate Digit Verification of CAS Registry Number 6596-74: (6*6)+(5*5)+(4*9)+(3*6)+(2*7)+(1*4)=133 133 % 10 = 3 So 6596-74-3 is a valid CAS Registry Number.