Wolfram Function Repository

Instant-use add-on functions for the Wolfram Language

Function Repository Resource:

 ClosestPrime

Source Notebook

Find the prime integer closest to a number

Contributed by: Wolfram|Alpha Math Team

ResourceFunction["ClosestPrime"][n]

returns the prime number closest to n.

Details and Options

If the two primes nearest to n are equally distant, ResourceFunction["ClosestPrime"][n] returns the lower of the two.

Examples

Basic Examples (2) 

Find the closest prime to 100:

In[1]:=
ResourceFunction["ClosestPrime"][100]
Out[1]=

Find the closest prime to 15:

In[2]:=
ResourceFunction["ClosestPrime"][15]
Out[2]=

Properties and Relations (3) 

The input to ClosestPrime need not be an integer:

In[3]:=
ResourceFunction["ClosestPrime"][34.81]
Out[3]=

Symbolically specified numbers may also be used:

In[4]:=
ResourceFunction["ClosestPrime"][8 Pi]
Out[4]=

Negative numbers are not considered to be prime. Inputting a negative number will always return 2:

In[5]:=
ResourceFunction["ClosestPrime"][-10]
Out[5]=

ClosestPrime is similar but not identical to NextPrime. ClosestPrime[n] returns the prime number to closest to n, considering numbers less than, equal to, or greater than n. NextPrime[n] returns the closest prime number to n, considering only numbers greater than n:

In[6]:=
ResourceFunction["ClosestPrime"][14]
Out[6]=
In[7]:=
NextPrime[14]
Out[7]=

Publisher

Wolfram|Alpha Math Team

Version History

  • 2.0.0 – 23 March 2023
  • 1.1.0 – 12 May 2021
  • 1.0.0 – 10 April 2020

Related Resources

License Information