The CAS Registry Mumber 16117-23-0 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,6,1,1 and 7 respectively; the second part has 2 digits, 2 and 3 respectively. Calculate Digit Verification of CAS Registry Number 16117-23: (7*1)+(6*6)+(5*1)+(4*1)+(3*7)+(2*2)+(1*3)=80 80 % 10 = 0 So 16117-23-0 is a valid CAS Registry Number.