The CAS Registry Mumber 118001-81-3 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,1,8,0,0 and 1 respectively; the second part has 2 digits, 8 and 1 respectively. Calculate Digit Verification of CAS Registry Number 118001-81: (8*1)+(7*1)+(6*8)+(5*0)+(4*0)+(3*1)+(2*8)+(1*1)=83 83 % 10 = 3 So 118001-81-3 is a valid CAS Registry Number.