December 30, 2023
3 mins read

Check if a number is prime or not using Python

prime numbers

This article explains how to tell if a number is prime or not using Python. In mathematics, a prime number is a natural number greater than 1 that has only two distinct divisors: 1 and itself. Prime numbers are important in many areas of mathematics, including number theory, cryptography, and probability theory.

Prime Numbers in Nature

Prime numbers are those numbers greater than 1 that have no divisor other than 1 and themselves. Although prime numbers are a mathematical construct, patterns and examples of prime numbers can be found in nature. Here are some examples:

  1. Number of petals in flowers:
  • Many flowers have a number of petals which is a prime number. For example, lilies with 3 petals, clovers with 3 leaflets, violets with 5 petals, etc.

2. Holes in mollusk shells:

  • Some marine mollusks have shells with a prime number of holes. For example, some species of snails have shells with 2, 3, or 5 holes.

3. Patterns on fruits:

  • When counting sections on fruits such as oranges or lemons, prime numbers are often found. For example, oranges often have 10 sections (a number divisible by 2 and 5), but some varieties have 8 or 12 sections, which are compound numbers.

4. Distribution of leaves on stems:

  • The number of spirals in the arrangement of leaves on stems of some plants often follows a pattern of prime numbers. This pattern helps maximize sun exposure and leaf arrangement efficiency.

5. Reproduction cycles of certain insects:

  • The breeding period of certain insects may follow prime-based cycles to minimize competition with other insects that have shorter breeding cycles.

6. Stripe Patterns in Animals:

  • Some animals, such as fish, have striped patterns on their skin that follow prime numbers. This can aid in camouflage and confusion of predators.

7. DNA Sequences:

  • In genetics, some DNA sequences have lengths that are prime numbers. These sequences play an important role in the formation and function of organisms.

These are just a few examples and exercises of the presence of prime numbers in nature. The distribution of prime numbers is an intriguing mathematical property that often manifests itself in various aspects of the natural world.

Looking for a Prime Number in Python

In Python, we can check whether a number is prime using  a for loop  or a while loop. Here’s some code in Python:

def es_primo(n):
"""
Returns True if the number n is prime, False otherwise.
Args:
n: The number to check.
Returns:
True if the number is prime, False otherwise.
"""
if n < 2:
return False
for i in range(2, int(n ** 0.5) + 1):
if n % i == 0:
return False
return True
if __name__ == "__main__":
n = int(input("Enter a number: "))
print(f"The number {n} is {'prime' if es_primo(n) else 'non-prime'}")

Here’s how this code works:

  • First, check if the number is less than 2. If so, it can’t be prime since it only has one divisor.
  • Then, iterate all the numbers from 2 to the square root of the given number. If you find a divisor, the number is not prime.
  • If you don’t find any divisors, the number is prime.

Here’s an example of how to use the code:

Enter a number: 5
The number 5 is prime

You can also write the code using a while loop:

def es_primo(n):
"""
Returns True if the number n is prime, False otherwise.
Args:
n: The number to check.
Returns:
True if the number is prime, False otherwise.
"""
if n < 2:
return False
i = 2
while i <= int(n ** 0.5):
if n % i == 0:
return False
i += 1
return True

This code works in the same way as the previous one, but it uses  a while loop  instead of a for loop.

Another way to identify a prime number without using loops

You can check if a number is prime without  using for or while loops  by using  the all function  in conjunction with the map function. Here’s an example of how to do it:

def es_primo(n):
return n > 1 and all(map(lambda x: n % x != 0, range(2, int(n**0.5) + 1)))
number = int(input("Enter a number to check if it's prime:"))
if es_primo(number):
print(f"{number} is a prime number.")
else:
print(f"{number} is not a prime number.")

In this code,  the function es_primo takes a number  n  and returns True if there is no divisor in the range of 2 to the square root of  n  that divides n exactly. The all function  is  responsible for verifying that this condition is true for all elements in the range. The map function  is used to apply the lambda condition to each element in the range.

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Avelino Dominguez

??‍? Biologist ??‍? Teacher ??‍? Technologist ? Statistician ? #SEO #SocialNetwork #Web #Data ♟Chess ? Galician

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