They all have factors
example
0: 0
1:1
2:1, 2
3:1, 3
etc.
There are 12 numbers less than 150 which have an odd number of factors: 1,4,9,16,25,36,49,64,81,100,121,144.
840
36
36
A whole number has an odd number of unique factors if and only if it is a perfect square. The perfect squares less than 10 are 0, 1, 4, and 9. Therefore, there are four whole numbers less than 10 that have an odd number of unique factors.
The three greatest whole numbers less than 200 that each have an odd number of factors are 144, 169 and 196.
the number 90 has the most factors under 100
360, 420 and 480 each have 24 factors.
There is no whole number less than zero.
less than
less than
less than