The CAS Registry Mumber 98684-82-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,8,6,8 and 4 respectively; the second part has 2 digits, 8 and 2 respectively. Calculate Digit Verification of CAS Registry Number 98684-82: (7*9)+(6*8)+(5*6)+(4*8)+(3*4)+(2*8)+(1*2)=203 203 % 10 = 3 So 98684-82-3 is a valid CAS Registry Number.