The CAS Registry Mumber 169543-49-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,6,9,5,4 and 3 respectively; the second part has 2 digits, 4 and 9 respectively. Calculate Digit Verification of CAS Registry Number 169543-49: (8*1)+(7*6)+(6*9)+(5*5)+(4*4)+(3*3)+(2*4)+(1*9)=171 171 % 10 = 1 So 169543-49-1 is a valid CAS Registry Number.