The CAS Registry Mumber 28224-89-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 2,8,2,2 and 4 respectively; the second part has 2 digits, 8 and 9 respectively. Calculate Digit Verification of CAS Registry Number 28224-89: (7*2)+(6*8)+(5*2)+(4*2)+(3*4)+(2*8)+(1*9)=117 117 % 10 = 7 So 28224-89-7 is a valid CAS Registry Number.