The CAS Registry Mumber 344349-05-9 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 3,4,4,3,4 and 9 respectively; the second part has 2 digits, 0 and 5 respectively. Calculate Digit Verification of CAS Registry Number 344349-05: (8*3)+(7*4)+(6*4)+(5*3)+(4*4)+(3*9)+(2*0)+(1*5)=139 139 % 10 = 9 So 344349-05-9 is a valid CAS Registry Number.