The CAS Registry Mumber 132398-81-3 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,3,2,3,9 and 8 respectively; the second part has 2 digits, 8 and 1 respectively. Calculate Digit Verification of CAS Registry Number 132398-81: (8*1)+(7*3)+(6*2)+(5*3)+(4*9)+(3*8)+(2*8)+(1*1)=133 133 % 10 = 3 So 132398-81-3 is a valid CAS Registry Number.