Atomic and nuclear properties of the neutron (n):

Quantity	Value	Units	Value	Units
Atomic number	0	n	n	n
Mass	+/- 1.008 664 915 95 (49)	u	+/- 939.565 420 52 (54)	MeV
Nuclear density	mmmfew x 1015	g cm-3	n	n

Mass values from 2018 CODATA
Mean life 878.4 ± 0.5 s (PDG 2024; error includes scale factor of 1.8)