范文：
Title: "21 in English"
The number 21 in English is written as "twentyone." It is a composite number, being the product of 3 and 7, and also the sum of 6 and 15. It is a unique number as it is the first number with a prime factorization that is not continuous. For example, 22 can be expressed as 2 x 11, but 21 requires two noncontinuous primes, 3 and 7, to form the product. In terms of numerology, the number 21 is often associated with transformation and spiritual growth.
10 Common Questions and Answers about "21 in English":
1. What is the number 21 called in English?
The number 21 is called "twentyone" in English.
2. How do you spell the number 21 in English?
The number 21 is spelled as "twentyone."
3. Is 21 a prime number?
No, 21 is not a prime number. It is a composite number because it can be divided evenly by 1, 3, 7, and 21.
4. What are the factors of 21?
The factors of 21 are 1, 3, 7, and 21.
5. How is the number 21 pronounced in English?
The number 21 is pronounced as "twentyone."
6. Is 21 an odd or even number?
21 is an odd number. Even numbers are divisible by 2, and since 21 is not divisible by 2 without a remainder, it is odd.
7. What is the square root of 21?
The square root of 21 is approximately 4.58257569495584.
8. Can 21 be expressed as a sum of two prime numbers?
Yes, 21 can be expressed as a sum of two prime numbers: 3 + 18, but 18 is not a prime number. However, 21 can be expressed as the sum of 3 and 18, which is not possible since 18 is not prime. The correct pair is 3 + 18, but since 18 is not prime, 21 cannot be expressed as the sum of two distinct prime numbers.
9. What is the ordinal form of the number 21?
The ordinal form of the number 21 is "twentyfirst."
10. In which numeral system is the number 21 written as "21"?
The number 21 is written as "21" in the decimal numeral system, which is the most commonly used numeral system in the world.
