23, 25, 27, 29... add two forever.
If you want a more mathematical notation, the nth odd number after 21 is
2n + 21
I don't know how else to say it, because there are infinite odd numbers above 21.
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There is an infinite number of prime numbers that are greater than 21. The next prime number after 21 is 23.
All odd numbers are the sum of two consecutive numbers. Odd multiples of 7 less than 25 are 7 and 21.
If an odd number has more than two factors then it is a composite number but if it has only two factors then it is a prime number. Although all prime numbers are odd except for 2 many more odd numbers are composite numbers having more than two factors as for example 21 is an odd number whose factors are 1, 3, 7 and 21.
Odd multiples of 7 less than 50 are numbers that are both odd and divisible by 7, and are less than 50. The odd multiples of 7 less than 50 are 7, 21, and 35. These numbers are odd because they are not divisible by 2, and they are multiples of 7 because they can be divided evenly by 7.
3, 5, 7, 11, and all other prime numbers greater than 1 are not square numbers. Neither are an infinite number of composite numbers, starting with 15, 21, 27, 33, etc. Of the first 40 odd numbers, only 1, 9, 25, and 49 are square numbers.