The CAS Registry Mumber 110808-05-4 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,1,0,8,0 and 8 respectively; the second part has 2 digits, 0 and 5 respectively. Calculate Digit Verification of CAS Registry Number 110808-05: (8*1)+(7*1)+(6*0)+(5*8)+(4*0)+(3*8)+(2*0)+(1*5)=84 84 % 10 = 4 So 110808-05-4 is a valid CAS Registry Number.