The CAS Registry Mumber 80980-30-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,0,9,8 and 0 respectively; the second part has 2 digits, 3 and 0 respectively. Calculate Digit Verification of CAS Registry Number 80980-30: (7*8)+(6*0)+(5*9)+(4*8)+(3*0)+(2*3)+(1*0)=139 139 % 10 = 9 So 80980-30-9 is a valid CAS Registry Number.