Given a number n, the task is to calculate its primorial. Primorial (denoted as Pn#) is product of first n prime numbers. Primorial of a number is similar to factorial of a number. In primorial, not all the natural numbers get multiplied only prime numbers are multiplied to calculate the primorial of a number. It is denoted with P#.
Input: n = 3 Output: 30 Priomorial = 2 * 3 * 5 = 30 As a side note, factorial is 2 * 3 * 4 * 5 Input: n = 5 Output: 2310 Primorial = 2 * 3 * 5 * 7 * 11
A naive approach is to check all numbers from 1 to n one by one is prime or not, if yes then store the multiplication in result, similarly store the result of multiplication of primes till n.
An efficient method is to find all the prime up-to n using Sieve of Sundaram and then just calculate the primorial by multiplying them all.
Primorial(P#) of 1 is 2 Primorial(P#) of 2 is 6 Primorial(P#) of 3 is 30 Primorial(P#) of 4 is 210 Primorial(P#) of 5 is 2310
This article is contributed by Sahil Chhabra (KILLER). 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 write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
- Check if a number is Primorial Prime or not
- Count number of triplets with product equal to given number with duplicates allowed
- Count number of trailing zeros in Binary representation of a number using Bitset
- Find minimum number to be divided to make a number a perfect square
- Number which has the maximum number of distinct prime factors in the range M to N
- Given number of matches played, find number of teams in tournament
- Minimum number of given powers of 2 required to represent a number
- Program to Convert Octal Number to Binary Number
- Queries on sum of odd number digit sums of all the factors of a number
- Super Ugly Number (Number whose prime factors are in given set)
- Find maximum number that can be formed using digits of a given number
- Build Lowest Number by Removing n digits from a given number
- Find the smallest number whose digits multiply to a given number n
- Check whether all the rotations of a given number is greater than or equal to the given number or not
- Represent a number as a sum of maximum possible number of Prime Numbers
Improved By : Mithun Kumar