The CAS Registry Mumber 137267-17-5 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,3,7,2,6 and 7 respectively; the second part has 2 digits, 1 and 7 respectively. Calculate Digit Verification of CAS Registry Number 137267-17: (8*1)+(7*3)+(6*7)+(5*2)+(4*6)+(3*7)+(2*1)+(1*7)=135 135 % 10 = 5 So 137267-17-5 is a valid CAS Registry Number.