Factors normally come in pairs, so most numbers have an even count of factors. Which of these numbers breaks that pattern and has an ODD number of factors?

To find every factor of a number, walk up from 1 and check each whole number — if it divides the number with no remainder, it is a factor. Factors come in **pairs**: if 4 is a factor of 12, so is 12 ÷ 4 = 3. So you only need to check up to the square root of the number to find them all. Factors of 12: $1\times 12,2\times 6,3\times 4$ — six factors total: 1, 2, 3, 4, 6, 12. Every number has 1 and itself as factors.