The CAS Registry Mumber 4108-18-3 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 4,1,0 and 8 respectively; the second part has 2 digits, 1 and 8 respectively. Calculate Digit Verification of CAS Registry Number 4108-18: (6*4)+(5*1)+(4*0)+(3*8)+(2*1)+(1*8)=63 63 % 10 = 3 So 4108-18-3 is a valid CAS Registry Number.