The CAS Registry Mumber 5597-66-0 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 5,5,9 and 7 respectively; the second part has 2 digits, 6 and 6 respectively. Calculate Digit Verification of CAS Registry Number 5597-66: (6*5)+(5*5)+(4*9)+(3*7)+(2*6)+(1*6)=130 130 % 10 = 0 So 5597-66-0 is a valid CAS Registry Number.