The CAS Registry Mumber 84889-97-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,4,8,8 and 9 respectively; the second part has 2 digits, 9 and 7 respectively. Calculate Digit Verification of CAS Registry Number 84889-97: (7*8)+(6*4)+(5*8)+(4*8)+(3*9)+(2*9)+(1*7)=204 204 % 10 = 4 So 84889-97-4 is a valid CAS Registry Number.