The CAS Registry Mumber 4566-73-8 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 4,5,6 and 6 respectively; the second part has 2 digits, 7 and 3 respectively. Calculate Digit Verification of CAS Registry Number 4566-73: (6*4)+(5*5)+(4*6)+(3*6)+(2*7)+(1*3)=108 108 % 10 = 8 So 4566-73-8 is a valid CAS Registry Number.