The CAS Registry Mumber 118087-75-5 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,1,8,0,8 and 7 respectively; the second part has 2 digits, 7 and 5 respectively. Calculate Digit Verification of CAS Registry Number 118087-75: (8*1)+(7*1)+(6*8)+(5*0)+(4*8)+(3*7)+(2*7)+(1*5)=135 135 % 10 = 5 So 118087-75-5 is a valid CAS Registry Number.