The CAS Registry Mumber 453-44-1 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 4,5 and 3 respectively; the second part has 2 digits, 4 and 4 respectively. Calculate Digit Verification of CAS Registry Number 453-44: (5*4)+(4*5)+(3*3)+(2*4)+(1*4)=61 61 % 10 = 1 So 453-44-1 is a valid CAS Registry Number.