2
2 is the only even prime number.
Where 2 fits
Why 2 is special
2 is the smallest prime and the only even one, making every other even number composite by definition.
2 in Numbers Around Us
2 is part of
Factors & digit properties
- Divisors (2)
- 1, 2
- Prime factorisation
- 2
- Digit sum
- 2
- Digital root
- 2
Representations
- Decimal
- 2
- Binary
- 10
- Octal
- 2
- Hexadecimal
- 2
- Roman numeral
- II
- Scientific notation
- 2.000 × 10^0
Other mathematical patterns
- Palindromic number
- Deficient number
- Factorial number
- Highly composite number
- Narcissistic (Armstrong) number
- Harshad (Niven) number
- Lucas number
- Sophie Germain prime
Related numbers & connections
2 is the atomic number of helium.
An octave is defined by a 2:1 frequency ratio — doubling a note's frequency raises it exactly one octave.
2 is the base of the binary (base-2) number system computing relies on.
Scientific association
- has scientific association withHelium (chemical element)
why?
Strength 0.50, confidence "high".
Numbers Around Us
- appears inOctave frequency ratio
why?
Strength 0.50, confidence "high".
Other connections
- is associated withBinary number system
why?
Strength 0.50, confidence "high".
Science
2 is the atomic number of helium, an inert noble gas.
DocumentedScience2 is the atomic number of helium, an inert noble gas.
DocumentedScience
Common questions
Is 2 a prime number?
Yes, 2 is prime — it has exactly two positive divisors: 1 and itself.
What are the factors of 2?
The factors of 2 are 1, 2.
What is 2 in Roman numerals?
2 in Roman numerals is II.
About this page's data
Mathematical facts:computed directly from the number's value — nothing to source or verify externally.
Contextual records: 2 reviewer-confirmed records, sourced and reviewed before publication.
Last reviewed: 15 July 2026