The CAS Registry Mumber 6439-49-2 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 6,4,3 and 9 respectively; the second part has 2 digits, 4 and 9 respectively. Calculate Digit Verification of CAS Registry Number 6439-49: (6*6)+(5*4)+(4*3)+(3*9)+(2*4)+(1*9)=112 112 % 10 = 2 So 6439-49-2 is a valid CAS Registry Number.