The CAS Registry Mumber 99808-96-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,9,8,0 and 8 respectively; the second part has 2 digits, 9 and 6 respectively. Calculate Digit Verification of CAS Registry Number 99808-96: (7*9)+(6*9)+(5*8)+(4*0)+(3*8)+(2*9)+(1*6)=205 205 % 10 = 5 So 99808-96-5 is a valid CAS Registry Number.