The CAS Registry Mumber 74789-86-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,4,7,8 and 9 respectively; the second part has 2 digits, 8 and 6 respectively. Calculate Digit Verification of CAS Registry Number 74789-86: (7*7)+(6*4)+(5*7)+(4*8)+(3*9)+(2*8)+(1*6)=189 189 % 10 = 9 So 74789-86-9 is a valid CAS Registry Number.