The CAS Registry Mumber 139004-18-5 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,3,9,0,0 and 4 respectively; the second part has 2 digits, 1 and 8 respectively. Calculate Digit Verification of CAS Registry Number 139004-18: (8*1)+(7*3)+(6*9)+(5*0)+(4*0)+(3*4)+(2*1)+(1*8)=105 105 % 10 = 5 So 139004-18-5 is a valid CAS Registry Number.