The CAS Registry Mumber 117175-27-6 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,1,7,1,7 and 5 respectively; the second part has 2 digits, 2 and 7 respectively. Calculate Digit Verification of CAS Registry Number 117175-27: (8*1)+(7*1)+(6*7)+(5*1)+(4*7)+(3*5)+(2*2)+(1*7)=116 116 % 10 = 6 So 117175-27-6 is a valid CAS Registry Number.