The CAS Registry Mumber 129731-48-2 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,9,7,3 and 1 respectively; the second part has 2 digits, 4 and 8 respectively. Calculate Digit Verification of CAS Registry Number 129731-48: (8*1)+(7*2)+(6*9)+(5*7)+(4*3)+(3*1)+(2*4)+(1*8)=142 142 % 10 = 2 So 129731-48-2 is a valid CAS Registry Number.