The CAS Registry Mumber 131941-97-4 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,3,1,9,4 and 1 respectively; the second part has 2 digits, 9 and 7 respectively. Calculate Digit Verification of CAS Registry Number 131941-97: (8*1)+(7*3)+(6*1)+(5*9)+(4*4)+(3*1)+(2*9)+(1*7)=124 124 % 10 = 4 So 131941-97-4 is a valid CAS Registry Number.