The CAS Registry Mumber 11104-97-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,1,1,0 and 4 respectively; the second part has 2 digits, 9 and 7 respectively. Calculate Digit Verification of CAS Registry Number 11104-97: (7*1)+(6*1)+(5*1)+(4*0)+(3*4)+(2*9)+(1*7)=55 55 % 10 = 5 So 11104-97-5 is a valid CAS Registry Number.