The CAS Registry Mumber 349-40-6 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 3,4 and 9 respectively; the second part has 2 digits, 4 and 0 respectively. Calculate Digit Verification of CAS Registry Number 349-40: (5*3)+(4*4)+(3*9)+(2*4)+(1*0)=66 66 % 10 = 6 So 349-40-6 is a valid CAS Registry Number.