The CAS Registry Mumber 91228-54-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,1,2,2 and 8 respectively; the second part has 2 digits, 5 and 4 respectively. Calculate Digit Verification of CAS Registry Number 91228-54: (7*9)+(6*1)+(5*2)+(4*2)+(3*8)+(2*5)+(1*4)=125 125 % 10 = 5 So 91228-54-5 is a valid CAS Registry Number.