The CAS Registry Mumber 66115-85-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,6,1,1 and 5 respectively; the second part has 2 digits, 8 and 5 respectively. Calculate Digit Verification of CAS Registry Number 66115-85: (7*6)+(6*6)+(5*1)+(4*1)+(3*5)+(2*8)+(1*5)=123 123 % 10 = 3 So 66115-85-3 is a valid CAS Registry Number.