The CAS Registry Mumber 80520-93-0 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,0,5,2 and 0 respectively; the second part has 2 digits, 9 and 3 respectively. Calculate Digit Verification of CAS Registry Number 80520-93: (7*8)+(6*0)+(5*5)+(4*2)+(3*0)+(2*9)+(1*3)=110 110 % 10 = 0 So 80520-93-0 is a valid CAS Registry Number.