The CAS Registry Mumber 18746-89-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,8,7,4 and 6 respectively; the second part has 2 digits, 8 and 9 respectively. Calculate Digit Verification of CAS Registry Number 18746-89: (7*1)+(6*8)+(5*7)+(4*4)+(3*6)+(2*8)+(1*9)=149 149 % 10 = 9 So 18746-89-9 is a valid CAS Registry Number.