The CAS Registry Mumber 80520-54-3 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, 5 and 4 respectively. Calculate Digit Verification of CAS Registry Number 80520-54: (7*8)+(6*0)+(5*5)+(4*2)+(3*0)+(2*5)+(1*4)=103 103 % 10 = 3 So 80520-54-3 is a valid CAS Registry Number.