The CAS Registry Mumber 118539-64-3 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,1,8,5,3 and 9 respectively; the second part has 2 digits, 6 and 4 respectively. Calculate Digit Verification of CAS Registry Number 118539-64: (8*1)+(7*1)+(6*8)+(5*5)+(4*3)+(3*9)+(2*6)+(1*4)=143 143 % 10 = 3 So 118539-64-3 is a valid CAS Registry Number.