7 13 27 29 which is not a prime number?
A prime number is a number that is divisible only by 1 and
itself; it has no other factors.
The factors of 7 are 1 and 7.
The factors of 13 are 1 and 13.
The factors of 27 are 1, 3, 9, and 27.
The factors of 29 are 1 and 29.
Therefore, 27 is the only one that is not a prime number.