The CAS Registry Mumber 90097-33-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,0,0,9 and 7 respectively; the second part has 2 digits, 3 and 3 respectively. Calculate Digit Verification of CAS Registry Number 90097-33: (7*9)+(6*0)+(5*0)+(4*9)+(3*7)+(2*3)+(1*3)=129 129 % 10 = 9 So 90097-33-9 is a valid CAS Registry Number.