The CAS Registry Mumber 181938-17-0 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,8,1,9,3 and 8 respectively; the second part has 2 digits, 1 and 7 respectively. Calculate Digit Verification of CAS Registry Number 181938-17: (8*1)+(7*8)+(6*1)+(5*9)+(4*3)+(3*8)+(2*1)+(1*7)=160 160 % 10 = 0 So 181938-17-0 is a valid CAS Registry Number.