On the scientific works of Dmitry Alexandrovich Popov

The present essay tells about the life and the scientific creativity of the brilliant Russian mathematician Dmitry Aleksandrovich Popov, who has celebrated his 80th anniversary in August, 2019. D.A. Popov made a considerable contribution to the mathematical foundations of the X-ray, ultrasonic and acoustic tomography, to the theory of the oscillating integrals estimations and to the problems concerning the distribution of lattice points in the plain circle and in the bodies of rotation. A special attention is paid to the recent results of the anniversarian that demonstrate a connection between the spectrum of Laplace operator on the fundamental domain of modular group with the distribution of primes.