The CAS Registry Mumber 86651-96-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,6,6,5 and 1 respectively; the second part has 2 digits, 9 and 6 respectively. Calculate Digit Verification of CAS Registry Number 86651-96: (7*8)+(6*6)+(5*6)+(4*5)+(3*1)+(2*9)+(1*6)=169 169 % 10 = 9 So 86651-96-9 is a valid CAS Registry Number.