Apophis orbital parameters have been improved on a basis of observations taken during the time span of 2004Рхз2011. The corresponding probability of its impact on the Earth in 2036 was proved to be vanishingly small. An attempt was made to reveal an influence of additional accelerations on Apophis motion. In so doing we consider A2 component of additional acceleration in orbital coordinate system, which is present in many near-Earth asteroids and some small main belt asteroids, as a manifestation of Yarkovsky effect. Our attempts to evaluate A2 for Apophis from observations using regularization process for solution of ill-conditioned systems of normal equations as well as other methods make it possible to conclude that A2 is positive. It means that Yarkovsky effect does not serve to increase the collision probability in 2036.