The CAS Registry Mumber 86120-20-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,6,1,2 and 0 respectively; the second part has 2 digits, 2 and 0 respectively. Calculate Digit Verification of CAS Registry Number 86120-20: (7*8)+(6*6)+(5*1)+(4*2)+(3*0)+(2*2)+(1*0)=109 109 % 10 = 9 So 86120-20-9 is a valid CAS Registry Number.