The CAS Registry Mumber 172967-05-4 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,7,2,9,6 and 7 respectively; the second part has 2 digits, 0 and 5 respectively. Calculate Digit Verification of CAS Registry Number 172967-05: (8*1)+(7*7)+(6*2)+(5*9)+(4*6)+(3*7)+(2*0)+(1*5)=164 164 % 10 = 4 So 172967-05-4 is a valid CAS Registry Number.