Formed as 五 × 万, with no sound change.
Common expressions
- 五万円: fifty thousand yen
- 五万人: fifty thousand people
- 五万部: fifty thousand copies
ごまんとある means "there are heaps of them" — an idiomatic exaggeration rather than a real count, and it is written in kana. そんな話はごまんとある "stories like that are a dime a dozen".