The CAS Registry Mumber 5289-88-3 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 5,2,8 and 9 respectively; the second part has 2 digits, 8 and 8 respectively. Calculate Digit Verification of CAS Registry Number 5289-88: (6*5)+(5*2)+(4*8)+(3*9)+(2*8)+(1*8)=123 123 % 10 = 3 So 5289-88-3 is a valid CAS Registry Number.