Hexakosioihexekontahexaphobia is a mouthful of a word, and it describes the fear of the number 666. However, if you're looking for a simpler word to describe this phobia, you may consider using "hexophobia" as an alternative. "Hexadecaphobia" is another synonym that you can use to describe the fear of number 16. For those who have a fear of the number 13, there's "triskaidekaphobia" to use instead of the common "friggatriskaidekaphobia." Ultimately, it's good to have synonyms available for complex terms like "hexakosioihexekontahexaphobia," as it makes communication clearer and easier for everyone involved.