The CAS Registry Mumber 564-44-3 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 4 respectively; the second part has 2 digits, 4 and 4 respectively. Calculate Digit Verification of CAS Registry Number 564-44: (5*5)+(4*6)+(3*4)+(2*4)+(1*4)=73 73 % 10 = 3 So 564-44-3 is a valid CAS Registry Number.