The CAS Registry Mumber 1138-51-8 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 1,1,3 and 8 respectively; the second part has 2 digits, 5 and 1 respectively. Calculate Digit Verification of CAS Registry Number 1138-51: (6*1)+(5*1)+(4*3)+(3*8)+(2*5)+(1*1)=58 58 % 10 = 8 So 1138-51-8 is a valid CAS Registry Number.