The CAS Registry Mumber 98718-97-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,8,7,1 and 8 respectively; the second part has 2 digits, 9 and 7 respectively. Calculate Digit Verification of CAS Registry Number 98718-97: (7*9)+(6*8)+(5*7)+(4*1)+(3*8)+(2*9)+(1*7)=199 199 % 10 = 9 So 98718-97-9 is a valid CAS Registry Number.