The CAS Registry Mumber 45988-18-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 4,5,9,8 and 8 respectively; the second part has 2 digits, 1 and 8 respectively. Calculate Digit Verification of CAS Registry Number 45988-18: (7*4)+(6*5)+(5*9)+(4*8)+(3*8)+(2*1)+(1*8)=169 169 % 10 = 9 So 45988-18-9 is a valid CAS Registry Number.