There are two different numbers. 3 and 7
Two.
21 has two prime factors.
There are 3 prime numbers from 21 to 35:23, 29 and 31
There are 21 two-digit prime numbers.
Four. The prime numbers between 10 and 21 are 11, 13, 17, and 19.
21 is not prime.
Do you mean, "What is the prime factorization of 21?"
21
The prime numbers from 21 to 40 are 23, 29, 31, and 37.
7 and 3 are prime numbers but 21 is a composite nuber
Out of those 100 numbers, 21 of them are prime numbers, so the remaining (100 - 21) = 79 are composite.
The prime factors of 21 are 3 x 7.