The CAS Registry Mumber 11138-16-2 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,1,1,3 and 8 respectively; the second part has 2 digits, 1 and 6 respectively. Calculate Digit Verification of CAS Registry Number 11138-16: (7*1)+(6*1)+(5*1)+(4*3)+(3*8)+(2*1)+(1*6)=62 62 % 10 = 2 So 11138-16-2 is a valid CAS Registry Number.