The CAS Registry Mumber 80520-45-2 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, 4 and 5 respectively. Calculate Digit Verification of CAS Registry Number 80520-45: (7*8)+(6*0)+(5*5)+(4*2)+(3*0)+(2*4)+(1*5)=102 102 % 10 = 2 So 80520-45-2 is a valid CAS Registry Number.