The CAS Registry Mumber 72167-36-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,2,1,6 and 7 respectively; the second part has 2 digits, 3 and 6 respectively. Calculate Digit Verification of CAS Registry Number 72167-36: (7*7)+(6*2)+(5*1)+(4*6)+(3*7)+(2*3)+(1*6)=123 123 % 10 = 3 So 72167-36-3 is a valid CAS Registry Number.