The CAS Registry Mumber 98120-28-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,8,1,2 and 0 respectively; the second part has 2 digits, 2 and 8 respectively. Calculate Digit Verification of CAS Registry Number 98120-28: (7*9)+(6*8)+(5*1)+(4*2)+(3*0)+(2*2)+(1*8)=136 136 % 10 = 6 So 98120-28-6 is a valid CAS Registry Number.