The factors of 26 are 1, 2, 13. And if you add them together (1+2+13) the answer is 16 which is less than 26 so it is an deficient number.
abundant
deficient
It is deficient.
it is abundant
abundant
13 is deficient.
deficient
It is deficient.
perfect
36 is abundant.
It's deficient
90 is abundant.