28
There is no one-digit number that is equal to both 14 and 28.
14³ - 28 = 2716
42 - 28 = 14
54 - 28 = 26
14 is less than 28 or 14 < 28
14 is less than 28 or 14 < 28
28
14 + 14 = 28
A number is perfect if all it's factors (barring itself) sum to make the original number. In this case, the factors of 28 are 1,2,4,7 and 14. Added up, these equal 28. Thus, 28 is a perfect number.
14
A silicon-28 atom has 14 protons, 14 neutrons, and 14 electrons. The number of protons determines the element (silicon in this case), the sum of protons and neutrons gives the atomic mass of the isotope (28 in this case), and the number of electrons balances the charge to make the atom electrically neutral.