In a parliamentary system, by contrast, the legislature holds supreme power. The prime minister is chosen by members of the legislature (Parliament) from among their own number and in practice is the leader of the majority party in the legislature.
There are 435 Representatives in the House of Representatives. The number of members in the House of Representatives is a different story and is based on population.
But the number 435, which was set in 1911 when the population reached 92 million, is completely arbitrary. The Constitution does not stipulate an upper limit to the number of representatives in the House. We could just as easily have 535 or 835 members. Through some legislative sleight-of-hand following the 1920 census, the House decided, contrary to established practice, not to increase its size.