Here is the list of common scientific constants for your reference, mostly from Physics or Chemistry.
Proton mass = 1.672621777 * 10^(-27) kg
Neutron mass = 1.674927351 * 10^(-27) kg
Electron mass / Electron rest mass = 9.10938291 * 10^(-31) kg
Muon mass = 1.8835312475 * 10^(-28) kg
Bohr radius = 5.291772109 * 10^(-11) m
Planck constant = 6.62606957 * 10^(-34) J s
Nuclear magneton = 5.05078353 * 10^(-27) J T^(-1)
Bohr magneton = 9.27400968 * 10^(-24) J T^(-1)
Rationalized planck constant = 1.054571726 * 10^(-34) J s
Fine-structure constant = 7.29735257 * 10^(-3)
Classical electron radius = 2.817940327 * 10^(-15) m
Compton wavelength = 2.426310239 * 10^(-12) m
Proton gyromagnetic ratio = 267,522,200.5 s^(-1) T^(-1)
Proton Compton wavelength = 1.321409856 * 10^(-15) m
Neutron Compton wavelength = 1.319590907 * 10^(-15) m
Rydberg constant = 10,973,731.57 m^(-1)
Atomic mass unit = 1.660538921 * 10^(-27) kg (1 u = 931 MeV)
Proton magnetic moment = 1.410606743 * 10^(-26) J T^(-1)
Electron magnetic moment = -9.284743 * 10^(-24) J T^(-1)
Neutron magnetic moment = -9.6623647 * 10^(-27) J T^(-1)
Muon magnetic moment = -4.49044807 * 10^(-26) J T^(-1)
Faraday constant = 96,485.3365 C mol^(-1)
Elementary charge = 1.602176565 * 10^(-19) C
Avogadro constant = 6.02214129 * 10^23 mol^(-1)
Boltzmann constant = 1.3806488 * 10^(-23) J K^(-1)
Molar volume of ideal gas = 0.022710953 m^3 mol^(-1)
Molar gas constant = 8.3144621 J mol^(-1) K^(-1)
Speed of light in vacuum = 299,792,458 m s^(-1)
First radiation constant = 3.74177153 * 10^(-16) W m^2
Second radiation constant = 0.01438777 m K
Stefan-Boltzmann constant / Stefan constant = 5.670373 * 10^(-8) W m^(-2) K^(-4)
Electric constant = 8.854187817 * 10^(-12) F m^(-1)
Magnetic constant = 1.256637061 * 10^(-6) N A^(-2)
Magnetic flux quantum = 2.067833758 * 10^(-15) Wb
Standard acceleration of gravity / Acceleration due to gravity = 9.80665 m s^(-2) (close to the Earth)
Conductance quantum = 7.748091735 * 10^(-5) S
Characteristic impedance of vacuum = 376.7303135 Ω
Celsius temperature = 273.15 K
Newtonian constant of gravitation / Universal gravitational constant = 6.67384 * 10^(-11) m^3 kg^(-1) s^(-2)
Standard atmosphere = 101,325 Pa
Permittivity of free space = 8.85 * 10^(-12) C^2 N^(-1) m^(-2)
Permeability of free space = 4π * 10^(-7) = 1.256637061 * 10^(-6) H m^(-1)
Astronomical unit = 1.5 * 10^11 m
Light year = 9.46 * 10^15 m
Parsec = 3.09 * 10^16 m = 3.26 ly = 206,265 AU