The CAS Registry Mumber 65165-99-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,5,1,6 and 5 respectively; the second part has 2 digits, 9 and 9 respectively. Calculate Digit Verification of CAS Registry Number 65165-99: (7*6)+(6*5)+(5*1)+(4*6)+(3*5)+(2*9)+(1*9)=143 143 % 10 = 3 So 65165-99-3 is a valid CAS Registry Number.