The CAS Registry Mumber 4535-54-0 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 4,5,3 and 5 respectively; the second part has 2 digits, 5 and 4 respectively. Calculate Digit Verification of CAS Registry Number 4535-54: (6*4)+(5*5)+(4*3)+(3*5)+(2*5)+(1*4)=90 90 % 10 = 0 So 4535-54-0 is a valid CAS Registry Number.