The CAS Registry Mumber 404-67-1 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 4,0 and 4 respectively; the second part has 2 digits, 6 and 7 respectively. Calculate Digit Verification of CAS Registry Number 404-67: (5*4)+(4*0)+(3*4)+(2*6)+(1*7)=51 51 % 10 = 1 So 404-67-1 is a valid CAS Registry Number.