# 251 (number)

 ← 250 251 252 →
Cardinal two hundred fifty-one
Ordinal 251st
(two hundred and fifty-first)
Factorization 251
Prime 54th
Roman numeral CCLI
Binary 111110112
Ternary 1000223
Quaternary 33234
Quinary 20015
Senary 10556
Octal 3738
Duodecimal 18B12
Vigesimal CB20
Base 36 6Z36

251 (two hundred [and] fifty-one) is the natural number between 250 and 252. It is also a prime number.

## In mathematics

251 is a Sophie Germain prime.[1] Every 5 × 5 matrix has exactly 251 square submatrices.[2] 251 is a de Polignac number, meaning that it is odd and cannot be formed by adding a power of two to a prime number.[3][4] It is the smallest number that can be formed in more than one way by summing three positive cubes:[5][6]

$251 = 2^3 + 3^3 + 6^3 = 1^3 + 5^3 + 5^3.$

## References

1. Kozek, Mark Robert (2007), Applications of Covering Systems of Integers and Goldbach's Conjecture for Monic Polynomials, PhD dissertation, University of South Carolina, p. 14, ISBN 9780549210207<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>.
2. Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value)..