Prime number is a positive natural number that has only two positive natural number divisors - one and the number itself.

Prime numbers are subset of natural numbers. A natural number is a positive natural number that has at least one positive divisor other than one or itself.

The number 1 is not a prime number by definition - it has only one divisor.

The number 0 is not a prime number - it is not a positive number and has infinite number of divisors.

The number 15 has divisors of 1,3,5,15 because:

15/1=15

15/3=5

15/5=3

15/15=1

So 15 is **not** a prime number.

The number 13 has only two divisors of 1,13.

13/1=13

13/13=1

So 13 is a prime number.

List of prime numbers up to 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 number 0 is not a prime number.

Zero is not a positive number and has infinite number of divisors.

The number 1 is not a prime number by definition.

One is has one divisor - itself.

The number 2 is a prime number.

Two has 2 natural number divisors - 1 and 2:

2 / 1 = 2

2 / 2 = 1

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- Numeral systems
- Percentage (%)
- Per-mille (‰)
- Parts-per million (ppm)
- Zero number
- Prime number
- e constant
- Fibonacci numbers
- Multiplication table