The CAS Registry Mumber 123333-40-4 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, 4 and 0 respectively. Calculate Digit Verification of CAS Registry Number 123333-40: (8*1)+(7*2)+(6*3)+(5*3)+(4*3)+(3*3)+(2*4)+(1*0)=84 84 % 10 = 4 So 123333-40-4 is a valid CAS Registry Number.