The CAS Registry Mumber 18831-79-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,8,8,3 and 1 respectively; the second part has 2 digits, 7 and 9 respectively. Calculate Digit Verification of CAS Registry Number 18831-79: (7*1)+(6*8)+(5*8)+(4*3)+(3*1)+(2*7)+(1*9)=133 133 % 10 = 3 So 18831-79-3 is a valid CAS Registry Number.