The CAS Registry Mumber 10324-28-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,0,3,2 and 4 respectively; the second part has 2 digits, 2 and 8 respectively. Calculate Digit Verification of CAS Registry Number 10324-28: (7*1)+(6*0)+(5*3)+(4*2)+(3*4)+(2*2)+(1*8)=54 54 % 10 = 4 So 10324-28-4 is a valid CAS Registry Number.