The CAS Registry Mumber 1028-04-2 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 1,0,2 and 8 respectively; the second part has 2 digits, 0 and 4 respectively. Calculate Digit Verification of CAS Registry Number 1028-04: (6*1)+(5*0)+(4*2)+(3*8)+(2*0)+(1*4)=42 42 % 10 = 2 So 1028-04-2 is a valid CAS Registry Number.