Number-Comma Format

local num = 5340789654

function format(n)
    local n, f = math['modf'](num)
    local s, cc = "", 0;
    for pos, c in (tostring(n):reverse()):gmatch("()(.)") do
        s = s .. c
        cc = cc + 1
        if cc % 3 == 0 and pos ~= tostring(n):len() then
            s = s .. ","
        end
    end
    return s:reverse() .. tostring(f):sub(2)
end

print(format(num))