The Disquisitiones Arithmeticae (Latin for "Arithmetical Investigations") is a textbook of number theory written in Latin by Carl Friedrich Gauss in 1798 when Gauss was 21 and first published in 1801 when he was 24. It is notable for having a revolutionary impact on the field of number theory as it not only turned the field truly rigorous and systematic but also paved the path for modern number theory. In this book, Gauss brought together and reconciled results in number theory obtained by mathematicians such as Fermat, Euler, Lagrange and Legendre and added many profound and original results of his own.