The CAS Registry Mumber 80031-16-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,0,0,3 and 1 respectively; the second part has 2 digits, 1 and 6 respectively. Calculate Digit Verification of CAS Registry Number 80031-16: (7*8)+(6*0)+(5*0)+(4*3)+(3*1)+(2*1)+(1*6)=79 79 % 10 = 9 So 80031-16-9 is a valid CAS Registry Number.