/usr/include/boost/numeric/conversion/ is in libboost1.62-dev 1.62.0+dfsg-5.
This file is owned by root:root, with mode 0o755.
..
/usr/include/boost/numeric/conversion/bounds.hpp
/usr/include/boost/numeric/conversion/cast.hpp
/usr/include/boost/numeric/conversion/conversion_traits.hpp
/usr/include/boost/numeric/conversion/converter.hpp
/usr/include/boost/numeric/conversion/converter_policies.hpp
/usr/include/boost/numeric/conversion/detail/
/usr/include/boost/numeric/conversion/detail/bounds.hpp
/usr/include/boost/numeric/conversion/detail/conversion_traits.hpp
/usr/include/boost/numeric/conversion/detail/converter.hpp
/usr/include/boost/numeric/conversion/detail/int_float_mixture.hpp
/usr/include/boost/numeric/conversion/detail/is_subranged.hpp
/usr/include/boost/numeric/conversion/detail/meta.hpp
/usr/include/boost/numeric/conversion/detail/numeric_cast_traits.hpp
/usr/include/boost/numeric/conversion/detail/old_numeric_cast.hpp
/usr/include/boost/numeric/conversion/detail/preprocessed/
/usr/include/boost/numeric/conversion/detail/preprocessed/numeric_cast_traits_common.hpp
/usr/include/boost/numeric/conversion/detail/preprocessed/numeric_cast_traits_long_long.hpp
/usr/include/boost/numeric/conversion/detail/sign_mixture.hpp
/usr/include/boost/numeric/conversion/detail/udt_builtin_mixture.hpp
/usr/include/boost/numeric/conversion/int_float_mixture.hpp
/usr/include/boost/numeric/conversion/int_float_mixture_enum.hpp
/usr/include/boost/numeric/conversion/is_subranged.hpp
/usr/include/boost/numeric/conversion/numeric_cast_traits.hpp
/usr/include/boost/numeric/conversion/sign_mixture.hpp
/usr/include/boost/numeric/conversion/sign_mixture_enum.hpp
/usr/include/boost/numeric/conversion/udt_builtin_mixture.hpp
/usr/include/boost/numeric/conversion/udt_builtin_mixture_enum.hpp