The CAS Registry Mumber 54493-54-8 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 4 respectively. Calculate Digit Verification of CAS Registry Number 54493-54: (7*5)+(6*4)+(5*4)+(4*9)+(3*3)+(2*5)+(1*4)=138 138 % 10 = 8 So 54493-54-8 is a valid CAS Registry Number.