The CAS Registry Mumber 11006-20-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,1,0,0 and 6 respectively; the second part has 2 digits, 2 and 0 respectively. Calculate Digit Verification of CAS Registry Number 11006-20: (7*1)+(6*1)+(5*0)+(4*0)+(3*6)+(2*2)+(1*0)=35 35 % 10 = 5 So 11006-20-5 is a valid CAS Registry Number.