This longitudinal study aims at identifying predictors of early numerical skills in six-year-old children. For this purpose, we collected data on cognitive factors (intelligence, working memory, rapid naming, phonological awareness) and social environment (socioeconomic status, migration background, home numeracy environment, home literacy environment, maternal self-estimation with regard to mathematics) in a sample of 132 five year olds. According to the results early numerical development is determined by a multifactorial set of conditions. Intelligence and phonological awareness do not contribute significantly to variance explanation. Instead, working memory (visual-spatial sketchpad) and the speed of retrieval from long-term memory make a significant contribution to variance explanation of early numerical skills. Interestingly, home numeracy environment and socio-economic status lead to significant additional explained variance of up to 12 %. We discuss the implications of our findings for diagnostic procedures and intervention methods for children at risk.