The CAS Registry Mumber 103395-51-3 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,3,3,9 and 5 respectively; the second part has 2 digits, 5 and 1 respectively. Calculate Digit Verification of CAS Registry Number 103395-51: (8*1)+(7*0)+(6*3)+(5*3)+(4*9)+(3*5)+(2*5)+(1*1)=103 103 % 10 = 3 So 103395-51-3 is a valid CAS Registry Number.