The CAS Registry Mumber 53530-66-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,3,5,3 and 0 respectively; the second part has 2 digits, 6 and 6 respectively. Calculate Digit Verification of CAS Registry Number 53530-66: (7*5)+(6*3)+(5*5)+(4*3)+(3*0)+(2*6)+(1*6)=108 108 % 10 = 8 So 53530-66-8 is a valid CAS Registry Number.