The CAS Registry Mumber 171824-23-0 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,7,1,8,2 and 4 respectively; the second part has 2 digits, 2 and 3 respectively. Calculate Digit Verification of CAS Registry Number 171824-23: (8*1)+(7*7)+(6*1)+(5*8)+(4*2)+(3*4)+(2*2)+(1*3)=130 130 % 10 = 0 So 171824-23-0 is a valid CAS Registry Number.