There are two completely different definitions of Cayley numbers. The first and most commonly encountered type of Cayley number is the eight elements in a Cayley algebra, more commonly known as octonions. A quantity which describes a Del Pezzo surface is sometimes also called a Cayley number (Coxeter 1973, p. 211).
Cayley Number
See also
Complex Number, Del Pezzo Surface, Octonion, Quaternion, Real NumberExplore with Wolfram|Alpha
References
Coxeter, H. S. M. Regular Polytopes, 3rd ed. New York: Dover, 1973.Referenced on Wolfram|Alpha
Cayley NumberCite this as:
Weisstein, Eric W. "Cayley Number." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/CayleyNumber.html