The CAS Registry Mumber 40018-16-4 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, 1 and 6 respectively. Calculate Digit Verification of CAS Registry Number 40018-16: (7*4)+(6*0)+(5*0)+(4*1)+(3*8)+(2*1)+(1*6)=64 64 % 10 = 4 So 40018-16-4 is a valid CAS Registry Number.