The CAS Registry Mumber 51138-49-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,1,1,3 and 8 respectively; the second part has 2 digits, 4 and 9 respectively. Calculate Digit Verification of CAS Registry Number 51138-49: (7*5)+(6*1)+(5*1)+(4*3)+(3*8)+(2*4)+(1*9)=99 99 % 10 = 9 So 51138-49-9 is a valid CAS Registry Number.