251

Previous  ... Next

Number

$251$ (two hundred and fifty-one) is:

The $54$th prime number.

The $1$st positive integer which can be expressed as the sum of $3$ cubes numbers in two or more different ways:

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

The larger of the $3$rd pair of primes whose prime gap is $10$:

$251 - 241 = 10$

The $4$th obstinate number after $1$, $127$, $149$

The $15$th trimorphic number after $1$, $4$, $5$, $6$, $9$, $24$, $25$, $49$, $51$, $75$, $76$, $99$, $125$, $249$:

$251^3 = 15 \, 813 \, \mathbf {251}$

The $18$th Sophie Germain prime after $2$, $3$, $5$, $11$, $23$, $29$, $41$, $53$, $83$, $89$, $113$, $131$, $173$, $179$, $191$, $233$, $239$:

$2 \times 251 + 1 = 503$, which is prime.

Also see

• Previous  ... Next: Obstinate Number

• Previous  ... Next: Sophie Germain Prime

• Previous  ... Next: Prime Number
• Previous  ... Next: Prime Gaps of 10

• Previous  ... Next: Trimorphic Number

Sources

• 1986: David Wells: Curious and Interesting Numbers ... (previous) ... (next): $251$
• 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $251$