The CAS Registry Mumber 118709-87-8 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, 8 and 7 respectively. Calculate Digit Verification of CAS Registry Number 118709-87: (8*1)+(7*1)+(6*8)+(5*7)+(4*0)+(3*9)+(2*8)+(1*7)=148 148 % 10 = 8 So 118709-87-8 is a valid CAS Registry Number.