The CAS Registry Mumber 1338818-61-3 includes 10 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 7 digits, 1,3,3,8,8,1 and 8 respectively; the second part has 2 digits, 6 and 1 respectively. Calculate Digit Verification of CAS Registry Number 1338818-61: (9*1)+(8*3)+(7*3)+(6*8)+(5*8)+(4*1)+(3*8)+(2*6)+(1*1)=183 183 % 10 = 3 So 1338818-61-3 is a valid CAS Registry Number.