The CAS Registry Mumber 99698-74-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,9,6,9 and 8 respectively; the second part has 2 digits, 7 and 4 respectively. Calculate Digit Verification of CAS Registry Number 99698-74: (7*9)+(6*9)+(5*6)+(4*9)+(3*8)+(2*7)+(1*4)=225 225 % 10 = 5 So 99698-74-5 is a valid CAS Registry Number.