8,400
It's already a numeric number
8400 :P
4020096 IS in numeric form.
8 in numeric numbers is VIII.
LXXV
Nineteen.
(VIII)
(XXII)
MMMMMMMMMMMMMD
XCIV
we write 5 in roman number like this :- V
A number must, surely, be numeric! I suggest writing it as 24000.