Given a number N, print all prime number smaller than or equal to N in reverse order .
For example, if N is 9, the output should be “7, 5, 3, 2”.
Input : N = 5 Output : 5 3 2 Input : N = 20 Output : 19 17 13 11 7 5 3 2
A simple solution is to traverse from N to 1. For every number, check if it is a prime using school method to check for prime. Print the number if it is prime.
An efficient solution is to use Sieve of Eratosthenes. We efficiently find all number from 1 to N, then print them.
Prime number in reverse order 23 19 17 13 11 7 5 3 2
Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.
- Print numbers such that no two consecutive numbers are co-prime and every three consecutive numbers are co-prime
- Program to print numbers from N to 1 in reverse order
- Print the nearest prime number formed by adding prime numbers to N
- Print prime numbers with prime sum of digits in an array
- Print all numbers whose set of prime factors is a subset of the set of the prime factors of X
- Absolute Difference between the Sum of Non-Prime numbers and Prime numbers of an Array
- Absolute difference between the Product of Non-Prime numbers and Prime numbers of an Array
- Absolute difference between the XOR of Non-Prime numbers and Prime numbers of an Array
- Count prime numbers that can be expressed as sum of consecutive prime numbers
- Print characters having prime frequencies in order of occurrence
- Sort only non-prime numbers of an array in increasing order
- Sort prime numbers of an array in descending order
- Prime numbers after prime P with sum S
- Check if a prime number can be expressed as sum of two Prime Numbers
- Sum of prime numbers without odd prime digits
- Check if a number is Prime, Semi-Prime or Composite for very large numbers
- Permutation of first N positive integers such that prime numbers are at prime indices
- Permutation of first N positive integers such that prime numbers are at prime indices | Set 2
- Count all prime numbers in a given range whose sum of digits is also prime
- Count numbers in a given range whose count of prime factors is a Prime Number
If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to email@example.com. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.