  The simplest integrands in the CHY formulation of scattering amplitudes are
constructed using the so-called Parke-Taylor functions. Parke-Taylor functions
also turn out to belong to a large class of rational functions known as MHV
leading singularities. In fact, Parke-Taylor functions correspond to planar MHV
leading singularities. In this note we study the behavior of CHY integrands
constructed using non-planar MHV leading singularities under collinear and
multi-particle factorization limits. General $n$-particle MHV leading
singularities are completely characterized by a set of $(n-2)$ triples of
particle labels. We give a simple operation on this combinatorial data which
"factors" the list into two sets of triples defining two lower point MHV
leading singularities. The fact that general MHV leading singularities form a
closed set under "multi-particle factorizations" is surprising from their gauge
theoretic origin.
