9.
There 25 primes less than 100: 2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97.
The twin primes that are greater than 20 but less than 30 are (23, 25) and (29, 31). However, since 25 is not prime, the only valid twin primes in that range are (29, 31). Twin primes are pairs of prime numbers that have a difference of two.
There are 168 prime numbers less than 1,000.
eight (8)
There are 8 twin primes less than 100. 3,5 : 5,7 : 11,13 : 17,19 : 29,31 : 41,43 : 59,61 : 71,73
472.
There are 25 primes smaller than 100.
Composite
The odd primes less than 20 are: 3 5 7 11 13 17 19
The only even prime number is... 2 !
There are an infinite number of primes greater than any number given.
59 and 53 are the two largest primes less than 60. 59+53 = 112