The CAS Registry Mumber 344-15-0 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 4 respectively; the second part has 2 digits, 1 and 5 respectively. Calculate Digit Verification of CAS Registry Number 344-15: (5*3)+(4*4)+(3*4)+(2*1)+(1*5)=50 50 % 10 = 0 So 344-15-0 is a valid CAS Registry Number.