What do we call the numbers that cannot be arranged into 2-row arrays?

Odd numbers or numbers without a multiple of 2 in them.

The numbers that cannot be arranged into 2-row arrays are called odd numbers. To understand why, let's first clarify what a 2-row array means. A 2-row array is an arrangement of numbers where the numbers are organized into two rows, with an equal number of elements in each row.

Now, let's consider the concept of odd numbers. Odd numbers are integers that are not divisible evenly by 2. In other words, when an odd number is divided by 2, there will always be a remainder of 1.

To determine if a number can be arranged into a 2-row array, we need to check if it is divisible by 2 or not. If a number is divisible by 2, it means it has a multiple of 2, and thus it can be arranged into a 2-row array. On the other hand, if a number is not divisible by 2, it is an odd number, and it cannot be arranged into a 2-row array.

Therefore, the numbers that cannot be arranged into 2-row arrays are referred to as odd numbers or numbers without a multiple of 2 in them.