The CAS Registry Mumber 339-74-2 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 3,3 and 9 respectively; the second part has 2 digits, 7 and 4 respectively. Calculate Digit Verification of CAS Registry Number 339-74: (5*3)+(4*3)+(3*9)+(2*7)+(1*4)=72 72 % 10 = 2 So 339-74-2 is a valid CAS Registry Number.