The CAS Registry Mumber 40018-13-1 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 3 respectively. Calculate Digit Verification of CAS Registry Number 40018-13: (7*4)+(6*0)+(5*0)+(4*1)+(3*8)+(2*1)+(1*3)=61 61 % 10 = 1 So 40018-13-1 is a valid CAS Registry Number.