Name the number of troops for troops per $1 billion being 2.45
create table table_30108346_1 (number_of_troops varchar, troops_per_$1_billion___usd___gdp varchar, PRIMARY KEY (number_of_troops))
select count(number_of_troops) from table_30108346_1 where troops_per_$1_billion___usd___gdp = "2.45"