The purpose of the present study was to understand how number writing in a class of low-income, pre-kindergarten children (N = 15) developed over the course of a school year, and to see what role that development played in their overall math readiness. The study used a mixed-methods approach. The target class was explicitly taught number writing as part of an early math intervention. Scores on a number writing inventory, and two math readiness assessments (Number Knowledge assessment, State of Florida VPK Assessment) were compared at the end of the year, both within the intervention group, and with a matched comparison group who did not participate in the intervention. The qualitative findings revealed that the characteristics necessary for preschool children to successfully write their numbers included: fine motor skills, cardinal and ordinal number knowledge, number symbol recognition, sensory tactile memory, and visual-spatial skills. Children demonstrated different paths and rates of success, but all made significant gains in their number writing abilities, especially when compared to those who did not receive the intervention. The quantitative findings confirmed that the children in the intervention outperformed those in the comparison group on number writing and number knowledge measures and revealed that number writing is predictive of early math knowledge overall, both on an individual and group level, suggesting that number writing is essential to overall math readiness and is a skill that can and should be taught. The findings further suggest that number writing is both a reliable indicator of overall early math knowledge, and an important driver of a young child's mathematical thinking.  [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]