The CAS Registry Mumber 81505-19-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,1,5,0 and 5 respectively; the second part has 2 digits, 1 and 9 respectively. Calculate Digit Verification of CAS Registry Number 81505-19: (7*8)+(6*1)+(5*5)+(4*0)+(3*5)+(2*1)+(1*9)=113 113 % 10 = 3 So 81505-19-3 is a valid CAS Registry Number.