The CAS Registry Mumber 80340-39-2 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,0,3,4 and 0 respectively; the second part has 2 digits, 3 and 9 respectively. Calculate Digit Verification of CAS Registry Number 80340-39: (7*8)+(6*0)+(5*3)+(4*4)+(3*0)+(2*3)+(1*9)=102 102 % 10 = 2 So 80340-39-2 is a valid CAS Registry Number.