Algebraliens are a species of sentient colorful symbols. The most notable members of this species are Four, X, and Two. Most of the letters are variables.


In BFB, algebraliens appear to be more sloppily hand-drawn figures of their symbol. Unlike normal characters, algebraliens are hand-drawn. They are drawn with a thick black outline, with one uniform color. Their eyes consist of a black dot (pupil) and the white circle surrounding it (sclera). Their arms and legs are also different, being drawn with width and a lighter color than their body.

In "X Finds Out His Value" (canonicity is debatable), algebraliens appear to be more geometrical, drawn with straight lines and curves.


Algebraliens seem to share a close relationship with one another, rather with non-algebraliens. Algebraliens also like to host competitions, or "games".


Numbers seem to be more flexible than objects. Being round and bulbous, numbers seem to be made out of a squishy material. From character to character, the material varies. Four has squishy material (as seen in BFB 1 when Liy squished him) and X has a dry sponge material (also as seen in BFB 1). The rest of the number's materials are unknown. Numbers are also said to not have gender "where [they] come from" (mentioned by Four in "Enter the Exit"). They are also covered in "numeric membrane" (as Coiny implied in BFB 17), which is an analogue for skin.


Numbers seem to have a range of abilities, greatly differing from the cast.

These include:

Numbers differ in abilities, some being weaker than others. Four has most of the abilities listed. While X is only limited to some abilities (Levitation, Construction, Regeneration). Two has the ability to give his powers to others, though if the other numbers can is unknown.

Algebraic evaluation

Numbers are able to perform a mathematical operation with each other, and other number-like objects. In "Four Goes Too Far", Four is multiplied with Donut (representing 0), with X meant to be a multiplicative sign, but he ran away.

Notable numbers


  • When Four and Donut were multiplied, Four was found as goo inside of Donut. This may mean when any number is multiplied by 0, they are combined into 0.
  • Numbers seem to come from another realm, outside of the BFDI space.
  • In "Enter the Exit", when Four goes to eliminate Roboty, he has the old straight outline he had in XFOHV.
  • Most of them appear as recommended characters in some BFB episodes.
    • In addition, there are also recommended characters who appear to be letters like X, despite never being confirmed as XFOHV characters, such as Y (pronounced "whY" in its recommendation), I, D, K, Z and G.
    • Weirdly enough, in BFB 15, there is a recommended character called Asterisk, which is designed like the number and letter characters, despite not being one of them by itself. It might be that way because X can also be considered as a sign of his own in some cases.
    • There is another recommended character which has similar features to Four called Fourn, but with the differences being that it is yellowish-green and has thorns all over it. It is unknown if it is a number or not, but if it is then there could be other numbers diverted from the main numbers with different names and appearances.
  • Numbers with two or more digits are connected into one, such as the case with Fourteen, with the 1 and the 4 connected together into 14.
  • The official name of the species was revealed when jacknjellify hit 700,000 subscribers.[1]
  • The colors of the numbers from 1 to 8 are apparently based on the Minesweeper number colorings.
  • A musical eighth note similar to math symbols appears in Lo-Fi Beats to Yoyle To — BFB 21 on Friday, July 3, but it's not clarified if they are a math symbol, Tune, or neither.







See also

Math symbols
Numbers: ZeroOneTwoThreeFourFiveSixSevenEightNineFourteen

Letters: DGIKXYZ

Other symbols: DonutPiAsteriskPlusInfinityFour and X put togetherVariations of Four


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