Problem 981. Find nearest prime number less than input number

Created by Reza Ahmadzadeh

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Find nearest prime number less than input number.

For example: if the input number is 125, then the nearest prime number which is less than this number is 113.

Be careful, in that 1 is not a prime number. So there is NO prime less than 2.

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774 Solutions
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Last Solution submitted on Jul 10, 2020

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@bmtran (Bryant Tran) on 10 Oct 2012

1 isn't a prime number

Disha on 31 Jul 2013

agree @bmtran...

Grzegorz Knor on 20 Sep 2013

You should correct the test suite. 1 isn't a prime number.

Vishal on 6 Oct 2014

Correct the test suite 1 is not prime number.

Daniel Pereira on 6 May 2016

1 is not a prime number, in order to fulfill with the fundamental theorem of arithmetic:

https://en.wikipedia.org/wiki/Fundamental_theorem_of_arithmetic

https://en.wikipedia.org/wiki/Prime_number#Primality_of_one

John D'Errico on 22 Feb 2018

I removed the test case where n==2, since 1 is indeed not a prime number. I also added a random test case, so the problem is not so easily cooked by knowing all the test cases.

Solution Comments

Solution 1243365

1 Comment

1 Comment

Yinghui Li on 1 Aug 2017

Well I think number 1 is not a prime number, but I need to pass the test. So I wander all the right answer may be possibly wrong since you have 1.

Solution 840982

1 Comment

1 Comment

eggart on 2 Mar 2016

IMHO 1 is not a prime, so that on input n=2 the correct answer should be [] and not 1.

Solution 752761

1 Comment

1 Comment

Takehiko KOBORI on 4 Oct 2015

これで正しいだろ。

Solution 489950

2 Comments

2 Comments

bainhome on 24 Aug 2014

you still not change the wrong test suite:4.1 is not a prime.

Gareth Lee on 30 Apr 2015

agree with bainhome

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math prime numbers

Problem 981. Find nearest prime number less than input number

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Last 200 Solutions

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Problem Recent Solvers251

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Problem 981. Find nearest prime number less than input number

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Last 200 Solutions

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