The CAS Registry Mumber 5323-23-9 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 5,3,2 and 3 respectively; the second part has 2 digits, 2 and 3 respectively. Calculate Digit Verification of CAS Registry Number 5323-23: (6*5)+(5*3)+(4*2)+(3*3)+(2*2)+(1*3)=69 69 % 10 = 9 So 5323-23-9 is a valid CAS Registry Number.