The CAS Registry Mumber 12039-40-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,2,0,3 and 9 respectively; the second part has 2 digits, 4 and 0 respectively. Calculate Digit Verification of CAS Registry Number 12039-40: (7*1)+(6*2)+(5*0)+(4*3)+(3*9)+(2*4)+(1*0)=66 66 % 10 = 6 So 12039-40-6 is a valid CAS Registry Number.