The CAS Registry Mumber 440-03-9 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 4,4 and 0 respectively; the second part has 2 digits, 0 and 3 respectively. Calculate Digit Verification of CAS Registry Number 440-03: (5*4)+(4*4)+(3*0)+(2*0)+(1*3)=39 39 % 10 = 9 So 440-03-9 is a valid CAS Registry Number.