The CAS Registry Mumber 3819-64-5 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 3,8,1 and 9 respectively; the second part has 2 digits, 6 and 4 respectively. Calculate Digit Verification of CAS Registry Number 3819-64: (6*3)+(5*8)+(4*1)+(3*9)+(2*6)+(1*4)=105 105 % 10 = 5 So 3819-64-5 is a valid CAS Registry Number.