The CAS Registry Mumber 131407-91-5 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,3,1,4,0 and 7 respectively; the second part has 2 digits, 9 and 1 respectively. Calculate Digit Verification of CAS Registry Number 131407-91: (8*1)+(7*3)+(6*1)+(5*4)+(4*0)+(3*7)+(2*9)+(1*1)=95 95 % 10 = 5 So 131407-91-5 is a valid CAS Registry Number.