The CAS Registry Mumber 18011-90-0 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,8,0,1 and 1 respectively; the second part has 2 digits, 9 and 0 respectively. Calculate Digit Verification of CAS Registry Number 18011-90: (7*1)+(6*8)+(5*0)+(4*1)+(3*1)+(2*9)+(1*0)=80 80 % 10 = 0 So 18011-90-0 is a valid CAS Registry Number.