The CAS Registry Mumber 12001-20-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,2,0,0 and 1 respectively; the second part has 2 digits, 2 and 0 respectively. Calculate Digit Verification of CAS Registry Number 12001-20: (7*1)+(6*2)+(5*0)+(4*0)+(3*1)+(2*2)+(1*0)=26 26 % 10 = 6 So 12001-20-6 is a valid CAS Registry Number.