The CAS Registry Mumber 128918-11-6 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,8,9,1 and 8 respectively; the second part has 2 digits, 1 and 1 respectively. Calculate Digit Verification of CAS Registry Number 128918-11: (8*1)+(7*2)+(6*8)+(5*9)+(4*1)+(3*8)+(2*1)+(1*1)=146 146 % 10 = 6 So 128918-11-6 is a valid CAS Registry Number.