The CAS Registry Mumber 181997-60-4 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,8,1,9,9 and 7 respectively; the second part has 2 digits, 6 and 0 respectively. Calculate Digit Verification of CAS Registry Number 181997-60: (8*1)+(7*8)+(6*1)+(5*9)+(4*9)+(3*7)+(2*6)+(1*0)=184 184 % 10 = 4 So 181997-60-4 is a valid CAS Registry Number.