The CAS Registry Mumber 131172-74-2 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,3,1,1,7 and 2 respectively; the second part has 2 digits, 7 and 4 respectively. Calculate Digit Verification of CAS Registry Number 131172-74: (8*1)+(7*3)+(6*1)+(5*1)+(4*7)+(3*2)+(2*7)+(1*4)=92 92 % 10 = 2 So 131172-74-2 is a valid CAS Registry Number.