The CAS Registry Mumber 1439-71-0 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 1,4,3 and 9 respectively; the second part has 2 digits, 7 and 1 respectively. Calculate Digit Verification of CAS Registry Number 1439-71: (6*1)+(5*4)+(4*3)+(3*9)+(2*7)+(1*1)=80 80 % 10 = 0 So 1439-71-0 is a valid CAS Registry Number.