In this paper, the effects of the online learning of the mathematical area of divisibility are studied, by comparing the achievements of students who have learned this mathematical topic in the online and in-class environments. Data for this study were collected in seven schools at the beginning of the seventh grade of elementary education, with 383 participants aged 12 to 13. The test with four questions was designed according to the standards and levels set by APOSO (Agency for Pre-Primary, Primary, and Secondary Education in Bosnia and Herzegovina). Data were analyzed using a two-sample t-test and a Chi-square test. The results highlighted that there was no statistical difference in the total scores between the students who learned divisibility in the in-class environment and those who learned it in the online environment. When comparing students' achievement in each question separately, statistical difference appeared only in the question of the highest level according to APOSO. The mistakes that students made when solving divisibility problems were also part of this research.