The CAS Registry Mumber 68321-43-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,8,3,2 and 1 respectively; the second part has 2 digits, 4 and 3 respectively. Calculate Digit Verification of CAS Registry Number 68321-43: (7*6)+(6*8)+(5*3)+(4*2)+(3*1)+(2*4)+(1*3)=127 127 % 10 = 7 So 68321-43-7 is a valid CAS Registry Number.