By Newton's Law of Universal Gravitation, there is the gravitational forces between any bodies having mass. Each body attracts another body, and the direction of this force is along the straight line that goes through the bodies.

The magnitude of this force is `G*(m_1*m_2)/R^2,` where `m_1` and `m_2` are the masses, `R` is the distance and `G approx 6.7*10^(-11) (N*m^2)/(kg)^2` is the universal constant called gravitational constant.

The bodies are considered to be small with respect to the distance (point masses). For a bodies of a complex shape it is necessary to consider small pieces and add up forces.

Earth and the Sun may be considered as point masses. The mass of Earth is about `6*10^24 kg,` the mass of the Sun is about `2*10^30 kg` and the distance is about `1.5*10^11 m.` So the force is

`6.7*10^(-11)*6*10^24*2*10^30/(2.25*10^22)=3.6*10^22(N).`

This is the answer.