20
If I understand the question correctly, the digits 1, 2, 3, 4 and 5 appear the same number of times.
Yes. Every prime number appears in its own times table. But it does not appear in any other.
12 and 28
The mode is the number that occurs most often in a list. As both numbers appear the same amount of times, there is no mode.
180
That they are not perfect squares.
42 hoe
5 times
20
20
20
If I understand the question correctly, the digits 1, 2, 3, 4 and 5 appear the same number of times.
Each prime factor will appear an even number of times.
140
Single digit numbers is not correct. Squares of numbers will appear odd number of times in a multiplication table: 1², 2², 3², 4², 5², 7², etc....
5 times, simple maths