Function Return Help? attempt to concatenate string with function

The error is on line 29, trying to set the name so in another script it can tell if the part touched anything. I am purposely doing this on the client side. If there is anyway I can do this inside this script keeping it on the client, let me know. Here is my local script, inside a tool:

local gun = script.Parent
local ammo = game.ReplicatedStorage.NormalGunAmmo
local ActiveBullets = game.Workspace.ActiveBullets

local player = game.Players.LocalPlayer
local mouse = player:GetMouse()

local debounce = false
local count = 0

local function number()
    for i,v in pairs(ActiveBullets:GetChildren())do
        count = count+1
    end
    return count
end

gun.Activated:Connect(function()
    if debounce == false then
        debounce = true
        local bullet = ammo:Clone()
        bullet.CFrame = gun.Handle.CFrame

        local BodyVelocity = Instance.new("BodyVelocity",bullet)
        BodyVelocity.P = Vector3.new(10000,10000,10000)
        BodyVelocity.Velocity = mouse.Hit.LookVector * 100

        bullet.Parent = ActiveBullets
        bullet.Name = "Bullet"..number
        wait(.75)
        debounce = false
    end
end)

Error is in the title, and again, it occurs on line 29 trying to set the name, thanks!