The number 1. There are th roots of unity, known as the de Moivre numbers.
Unity
See also
1, Monad, Primitive Root of UnityExplore with Wolfram|Alpha
References
Wells, D. The Penguin Dictionary of Curious and Interesting Numbers. Middlesex, England: Penguin Books, pp. 30-32, 1986.Referenced on Wolfram|Alpha
UnityCite this as:
Weisstein, Eric W. "Unity." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Unity.html