The CAS Registry Mumber 161105-12-0 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,6,1,1,0 and 5 respectively; the second part has 2 digits, 1 and 2 respectively. Calculate Digit Verification of CAS Registry Number 161105-12: (8*1)+(7*6)+(6*1)+(5*1)+(4*0)+(3*5)+(2*1)+(1*2)=80 80 % 10 = 0 So 161105-12-0 is a valid CAS Registry Number.