The CAS Registry Mumber 128302-84-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,8,3,0 and 2 respectively; the second part has 2 digits, 8 and 4 respectively. Calculate Digit Verification of CAS Registry Number 128302-84: (8*1)+(7*2)+(6*8)+(5*3)+(4*0)+(3*2)+(2*8)+(1*4)=111 111 % 10 = 1 So 128302-84-1 is a valid CAS Registry Number.