The CAS Registry Mumber 121884-64-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,1,8,8 and 4 respectively; the second part has 2 digits, 6 and 4 respectively. Calculate Digit Verification of CAS Registry Number 121884-64: (8*1)+(7*2)+(6*1)+(5*8)+(4*8)+(3*4)+(2*6)+(1*4)=128 128 % 10 = 8 So 121884-64-8 is a valid CAS Registry Number.