The CAS Registry Mumber 131342-51-3 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,3,1,3,4 and 2 respectively; the second part has 2 digits, 5 and 1 respectively. Calculate Digit Verification of CAS Registry Number 131342-51: (8*1)+(7*3)+(6*1)+(5*3)+(4*4)+(3*2)+(2*5)+(1*1)=83 83 % 10 = 3 So 131342-51-3 is a valid CAS Registry Number.