The CAS Registry Mumber 65997-16-2 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,5,9,9 and 7 respectively; the second part has 2 digits, 1 and 6 respectively. Calculate Digit Verification of CAS Registry Number 65997-16: (7*6)+(6*5)+(5*9)+(4*9)+(3*7)+(2*1)+(1*6)=182 182 % 10 = 2 So 65997-16-2 is a valid CAS Registry Number.