The CAS Registry Mumber 9030-53-9 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 9,0,3 and 0 respectively; the second part has 2 digits, 5 and 3 respectively. Calculate Digit Verification of CAS Registry Number 9030-53: (6*9)+(5*0)+(4*3)+(3*0)+(2*5)+(1*3)=79 79 % 10 = 9 So 9030-53-9 is a valid CAS Registry Number.