The CAS Registry Mumber 6528-45-6 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 6,5,2 and 8 respectively; the second part has 2 digits, 4 and 5 respectively. Calculate Digit Verification of CAS Registry Number 6528-45: (6*6)+(5*5)+(4*2)+(3*8)+(2*4)+(1*5)=106 106 % 10 = 6 So 6528-45-6 is a valid CAS Registry Number.