The CAS Registry Mumber 86869-55-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,6,8,6 and 9 respectively; the second part has 2 digits, 5 and 5 respectively. Calculate Digit Verification of CAS Registry Number 86869-55: (7*8)+(6*6)+(5*8)+(4*6)+(3*9)+(2*5)+(1*5)=198 198 % 10 = 8 So 86869-55-8 is a valid CAS Registry Number.