This is the 1887th most frequent Russian word.
полтора
"Полтора" means "one and a half" in English.
Here, 'полтора' is used to express a quantity of time in hours, which is a neuter noun in Russian, thus matching the form 'полтора'.
Мне понадобится полтора часа, чтобы закончить работу.
It will take me one and a half hours to finish the job.
In this sentence, 'полторы' is used to quantify weight in kilograms, a feminine noun in Russian, hence using the feminine form 'полторы'.
Он купил полторы килограмма яблок.
He bought one and a half kilograms of apples.
Here, 'полтора' is applied to distance in kilometers, a masculine noun in Russian, therefore using the neuter form 'полтора'.