10, 20, 30, 40, 50, 60, 70, 80, 90
1 is not a prime number, so it wouldn't be present in any prime factorization. Prime numbers don't really have factorizations, that is, the factorization is the number itself. There are prime numbers greater than 100.
Prime factorization refers to whole numbers, not fractions. 100/50 = 2, which is already prime and therefore has no prime factorization other than itself.
There are 35 prime numbers less than 150.
There are 15 prime numbers less than 50
There are 48 prime numbers less than 220.
There are 27 prime numbers less than 102.
They are 239 prime numbers less than 1500.
Usually, but not necessarily and not if they're prime. All prime numbers have the same number of factors.
There are 25 prime numbers less than 100
2, 3 and 5 are prime numbers that are less than 7
the greatest prime numbers that is less than 100 = 97