The CAS Registry Mumber 54493-53-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,4,4,9 and 3 respectively; the second part has 2 digits, 5 and 3 respectively. Calculate Digit Verification of CAS Registry Number 54493-53: (7*5)+(6*4)+(5*4)+(4*9)+(3*3)+(2*5)+(1*3)=137 137 % 10 = 7 So 54493-53-7 is a valid CAS Registry Number.