The CAS Registry Mumber 80673-06-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,0,6,7 and 3 respectively; the second part has 2 digits, 0 and 6 respectively. Calculate Digit Verification of CAS Registry Number 80673-06: (7*8)+(6*0)+(5*6)+(4*7)+(3*3)+(2*0)+(1*6)=129 129 % 10 = 9 So 80673-06-9 is a valid CAS Registry Number.