The CAS Registry Mumber 55344-34-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,5,3,4 and 4 respectively; the second part has 2 digits, 3 and 4 respectively. Calculate Digit Verification of CAS Registry Number 55344-34: (7*5)+(6*5)+(5*3)+(4*4)+(3*4)+(2*3)+(1*4)=118 118 % 10 = 8 So 55344-34-8 is a valid CAS Registry Number.