Math symbols, also called algebraliens, are a species of sentient colorful symbols. The most notable members of this species are Four, X, Two, and Seven. Most of the letters are variables.


In BFB, math symbols 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), math symbols appear to be more geometrical, drawn with straight lines and curves.


Math symbols seem to share a close relationship with one another, rather with non-math symbols. Math symbols 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.
  • The number characters have also made at least one cameo in the BFDI universe, whether as recommended characters in some BFB episodes or as actual characters in videos featuring the Algebraliens, such as JacknJellify's 600,000, 700,000 and 800,000 subscribers specials.
    • 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 ,G, E, J (recommended by Jaysillyboy), F and T.
    • Weirdly enough, there are also some recommended characters that are neither numbers or letters, but other symbols, such as Asterisk, Pi (A Greek letter, but it's universally used as a math symbol), Plus , Ellipsis, Turned A (The symbol of universal quantification) and other variations of Four. Another one of them, NintySix, is a combination of the digits 6 and 9 together, possibly due to the misspelling of the number Ninety Six.
    • Asides from the many variations of Four which are seen as recommended characters throughout the series, there is another recommended character called Four and x put together. While it isn't considered as a number by itself, it does have the number characters' design, adding to the fact that it's a combination of the most noticeable ones, Four and x.
  • 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, and One Million, with the 1 connected together with the six 0's into 1000000.
  • 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.
    • It is possible that the color of 0 as well, based on the empty silver squares that you get sometimes in Minesweeper.
  • 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.
  • There is also another Algebralien character created by JacknJellify: Infinity. While they didn't appear in any video and aren't considered an official character, they did appear in JacknJellify's Tweet celebrating Autism Acceptance Day 2020.
  • Some Algebraliens can be armless, legless or even have a multitude of them, as supposed to One in BFB 25 or Million in BFB 27.
  • Some Algebraliens can have 2 or more variations, such as D, a recommended character from "Don't Dig Straight Down", and d, a recommended character from "Uprooting Everything".





See also


Math symbols
Numbers: ZeroOneTwoThreeFourFiveSixSevenEightNineFourteenOne Million


Other symbols: DonutPiAsteriskPlusInfinityFour and X put togetherNintySixVariations of Four


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