The CAS Registry Mumber 171367-33-2 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,7,1,3,6 and 7 respectively; the second part has 2 digits, 3 and 3 respectively. Calculate Digit Verification of CAS Registry Number 171367-33: (8*1)+(7*7)+(6*1)+(5*3)+(4*6)+(3*7)+(2*3)+(1*3)=132 132 % 10 = 2 So 171367-33-2 is a valid CAS Registry Number.