The potential benefits from the introduction of programming environments such as "Scratch" for learning mathematics has reactivated research in this area. Nonetheless, there are few studies which attempt to analyse their influence at the stage of Primary Education. We present the results of a quasi-experimental piece of research with sixth-grade students which studies the influence of "Scratch" both on the acquisition of mathematical concepts, and on the development of computational thinking. The experiment consisted of two different phases, a programming phase linked to the instruction in "Scratch" and focused on the acquisition of basic concepts of computational thinking (sequences, iterations, conditionals, and events-handling), and a mathematical phase completely oriented towards the resolution of mathematical tasks. In particular, the mathematical phase focused on word problems whose resolution involves the use of the least common multiple and the greatest common divisor. In order to evaluate the aims of the study, results from tests before and after instruction, both in computational thinking and in the mathematical standards, were compared. The results seem to indicate that "Scratch" can be used to develop both students' mathematical ideas and computational thinking.