The CAS Registry Mumber 123333-36-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,3,3,3 and 3 respectively; the second part has 2 digits, 3 and 6 respectively. Calculate Digit Verification of CAS Registry Number 123333-36: (8*1)+(7*2)+(6*3)+(5*3)+(4*3)+(3*3)+(2*3)+(1*6)=88 88 % 10 = 8 So 123333-36-8 is a valid CAS Registry Number.