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31 is a prime number from 1-100. 31 has 2 factors, 1 and 31. It is said to be a number wherein when digits are added together, they make a composite number. It is the eleventh prime number, and the eleventh prime number from 1-100. ## Proofs

• 1 can divide 31
• 2 cannot
• 3 cannot
• 4 - 28 cannot
• 29 cannot
• 30 also cannot
• 31 can divide itself

## ​Relationship with other odd numbers

### The numbers before

• The previous odd number, 29, is a prime number.
• There are no odd numbers between 29 and 31. As a result, they are twin primes.
• Before 29, the previous two odd numbers are 25 and 27. 25 is a square number, being 52 = 25. 27 is a cube number, being 33 = 27.
• The prime number previous to 29 is 23.

### The numbers after

• The next odd number, 33, is not a prime number. It is divisible by 3 and 11.
• The next odd number, 35, is also not a prime number. It is divisible by 5 and 7.
• 37, the odd number following 35, is a prime number.
• 31 and 37 are six numbers apart; therefore, they are sexy primes.
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