The CAS Registry Mumber 81618-03-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,1,6,1 and 8 respectively; the second part has 2 digits, 0 and 3 respectively. Calculate Digit Verification of CAS Registry Number 81618-03: (7*8)+(6*1)+(5*6)+(4*1)+(3*8)+(2*0)+(1*3)=123 123 % 10 = 3 So 81618-03-3 is a valid CAS Registry Number.