4

* 4.1 and 4.2
* 4-DAC
* 3 & 4
* 4 Unnamed Marines
* Agent 47
* Z 4195
* Agent 4
* Squad 404
* Yokosuka 467
* HK-47
* WAC-47
* WAC-47
* I-400
* I-402
* Four
== Roman Numerals ==
* Jarvan IV
* King Baldwin IV
* Garth Fitzgerald IV
* Stanley Yelnats IV
* Thester Carbomb IV
== SCPs ==
* SCP-451
* SCP-4017
* SCP-4128
* SCP-4640
* SCP-4239-1
* SCP-4606
* SCP-4793
* SCP-4999
* SCP-4494
* SCP-4051
* SCP-492