The CAS Registry Mumber 84598-88-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,4,5,9 and 8 respectively; the second part has 2 digits, 8 and 8 respectively. Calculate Digit Verification of CAS Registry Number 84598-88: (7*8)+(6*4)+(5*5)+(4*9)+(3*8)+(2*8)+(1*8)=189 189 % 10 = 9 So 84598-88-9 is a valid CAS Registry Number.