The CAS Registry Mumber 11126-20-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,1,1,2 and 6 respectively; the second part has 2 digits, 2 and 0 respectively. Calculate Digit Verification of CAS Registry Number 11126-20: (7*1)+(6*1)+(5*1)+(4*2)+(3*6)+(2*2)+(1*0)=48 48 % 10 = 8 So 11126-20-8 is a valid CAS Registry Number.