The CAS Registry Mumber 80309-54-2 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,0,3,0 and 9 respectively; the second part has 2 digits, 5 and 4 respectively. Calculate Digit Verification of CAS Registry Number 80309-54: (7*8)+(6*0)+(5*3)+(4*0)+(3*9)+(2*5)+(1*4)=112 112 % 10 = 2 So 80309-54-2 is a valid CAS Registry Number.