251
+251 is the international calling code for Ethiopia.
- Odd
- Prime
Where 251 fits
Why 251 is special
Ethiopia uses its own calendar, which runs seven to eight years behind the Gregorian one and has thirteen months. A country's telephone code is ordinary; its calendar is one of the few national ones still in everyday official use.
251 is part of
Factors & digit properties
- Divisors (2)
- 1, 251
- Prime factorisation
- 251
- Digit sum
- 8
- Digital root
- 8
Representations
- Decimal
- 251
- Binary
- 11111011
- Octal
- 373
- Hexadecimal
- fb
- Roman numeral
- CCLI
- Scientific notation
- 2.510 × 10^2
Other mathematical patterns
- Deficient number
- Sophie Germain prime
Related numbers & connections
Eritrea separated from Ethiopia in 1993 after a thirty-year war. Eritrea has among the lowest internet penetration in the world, which is state policy rather than infrastructure.
View 291 →Geography
+251 reaches Ethiopia, in the 2x block covering Africa. Ethiopia is also one of very few countries running its own calendar in official daily use, currently seven to eight years behind the Gregorian year.
DocumentedGeographyGeography: Ethiopia
Common questions
Is 251 a prime number?
Yes, 251 is prime — it has exactly two positive divisors: 1 and itself.
What are the factors of 251?
The factors of 251 are 1, 251.
What is 251 in Roman numerals?
251 in Roman numerals is CCLI.
About this page's data
Mathematical facts:computed directly from the number's value — nothing to source or verify externally.
Contextual records: 1 reviewer-confirmed record, sourced and reviewed before publication.
Last reviewed: 3 August 2026