The CAS Registry Mumber 562-66-3 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 5,6 and 2 respectively; the second part has 2 digits, 6 and 6 respectively. Calculate Digit Verification of CAS Registry Number 562-66: (5*5)+(4*6)+(3*2)+(2*6)+(1*6)=73 73 % 10 = 3 So 562-66-3 is a valid CAS Registry Number.