The CAS Registry Mumber 33021-69-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 3,3,0,2 and 1 respectively; the second part has 2 digits, 6 and 9 respectively. Calculate Digit Verification of CAS Registry Number 33021-69: (7*3)+(6*3)+(5*0)+(4*2)+(3*1)+(2*6)+(1*9)=71 71 % 10 = 1 So 33021-69-1 is a valid CAS Registry Number.