The CAS Registry Mumber 3288-63-9 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 3,2,8 and 8 respectively; the second part has 2 digits, 6 and 3 respectively. Calculate Digit Verification of CAS Registry Number 3288-63: (6*3)+(5*2)+(4*8)+(3*8)+(2*6)+(1*3)=99 99 % 10 = 9 So 3288-63-9 is a valid CAS Registry Number.