The CAS Registry Mumber 40018-09-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 4,0,0,1 and 8 respectively; the second part has 2 digits, 0 and 9 respectively. Calculate Digit Verification of CAS Registry Number 40018-09: (7*4)+(6*0)+(5*0)+(4*1)+(3*8)+(2*0)+(1*9)=65 65 % 10 = 5 So 40018-09-5 is a valid CAS Registry Number.