The CAS Registry Mumber 118709-90-3 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,1,8,7,0 and 9 respectively; the second part has 2 digits, 9 and 0 respectively. Calculate Digit Verification of CAS Registry Number 118709-90: (8*1)+(7*1)+(6*8)+(5*7)+(4*0)+(3*9)+(2*9)+(1*0)=143 143 % 10 = 3 So 118709-90-3 is a valid CAS Registry Number.