It is: 21 because it has more than two factors
The numbers 13 and 29 are prime - the one composite number in that list is 27.
27 is not a prime number.
29 is a prime. 9, 21, and 27 are composites because they are multiples of 3.
21 is not a prime number because it is 3 x 7
29 is prime.
27
There is an infinite number of prime numbers that are greater than 21. The next prime number after 21 is 23.
From 10 to 30, there are 21 numbers.Six of them are prime numbers: 11, 13, 17, 19, 23, and 29.If you pick a number at random from 10 to 30, the probabilitythat it's a prime number is6/21 = 2/7 = 28.57% (rounded)
prime numbers above 13 = 17, 19, 23, 29, 31,...
39 is not a prime number. It can be divided by 3 and 13.
27
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.