The CAS Registry Mumber 5309-24-0 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 5,3,0 and 9 respectively; the second part has 2 digits, 2 and 4 respectively. Calculate Digit Verification of CAS Registry Number 5309-24: (6*5)+(5*3)+(4*0)+(3*9)+(2*2)+(1*4)=80 80 % 10 = 0 So 5309-24-0 is a valid CAS Registry Number.