The CAS Registry Mumber 211919-84-5 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 2,1,1,9,1 and 9 respectively; the second part has 2 digits, 8 and 4 respectively. Calculate Digit Verification of CAS Registry Number 211919-84: (8*2)+(7*1)+(6*1)+(5*9)+(4*1)+(3*9)+(2*8)+(1*4)=125 125 % 10 = 5 So 211919-84-5 is a valid CAS Registry Number.