The CAS Registry Mumber 18419-81-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,8,4,1 and 9 respectively; the second part has 2 digits, 8 and 1 respectively. Calculate Digit Verification of CAS Registry Number 18419-81: (7*1)+(6*8)+(5*4)+(4*1)+(3*9)+(2*8)+(1*1)=123 123 % 10 = 3 So 18419-81-3 is a valid CAS Registry Number.