11 is the fifth prime number and the first 2-digit prime. 11's prime factors are 1 and 11.
- Therefore 11 has exactly 2 integer factors, 11 and 1.
As an Exponent of Mersenne Number
211 - 1, which is the number 2,047, can be factored into 23 x 89, and therefore not a prime number.
Relationship with other odd numbers
The numbers before
- The previous odd number, 9, is a square number.
- The odd number previous to 9 is 7. 7 is a prime number.
- 7 and 11 are four numbers apart; therefore, they are cousin primes.
- The odd number previous to 7 is 5. 5 is a prime number.
- 5 and 11 are six numbers apart; therefore, they are sexy primes.
The numbers after
- The next odd number, 13, is a prime number.
- There are no odd numbers between 11 and 13. As a result, they are twin primes.
- 15, the odd number following 13, is not a prime number. It is divisible by 3 and 5.
- 17, the odd number following 15, is a prime number.
- 11 and 17 are six numbers apart; therefore, they are sexy primes.
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