Fear of new numbers.
Given the nature of infinity, there can be no “new numbers” so (at least debatably) neonumerophobia can't exist but, subjectively, a number could be “new” to an individual so there may be a need. Sceptical though mathematicians are likely to be, the notion of the “new number” has (in various ways) been explored in fiction including by science fiction (SF or SciFi) author & engineer Robert A Heinlein (1907–1988) in The Number of the Beast (1980), written during his “later period”. More challenging was Flatland: A Romance of Many Dimensions by English schoolmaster & Anglican priest Edwin Abbott Abbott (1838–1926) which was published under the pseudonym “A Square”, the layer of irony in that choice revealed as the protagonist begins to explore dimensions beyond his two-dimensional world (in Victorian England). Feminists note also Ursula K Le Guin’s (1929–2018) The Left Hand of Darkness (1969) in which was created an entirely new numerical system of “genderless" numbers”. That would induce fear in many.