The CAS Registry Mumber 118161-36-7 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,1,8,1,6 and 1 respectively; the second part has 2 digits, 3 and 6 respectively. Calculate Digit Verification of CAS Registry Number 118161-36: (8*1)+(7*1)+(6*8)+(5*1)+(4*6)+(3*1)+(2*3)+(1*6)=107 107 % 10 = 7 So 118161-36-7 is a valid CAS Registry Number.