4 (four) is a
number,
numeral and
digit
Digit may refer to:
Mathematics and science
* Numerical digit, as used in mathematics or computer science
** Hindu-Arabic numerals, the most common modern representation of numerical digits
* Digit (anatomy), the most distal part of a limb, such ...
. It is the
natural number following
3 and preceding
5. It is the smallest
semiprime and
composite number, and is
considered unlucky in many East Asian cultures.
In mathematics
Four is the smallest
composite number, its proper
divisors being and . Four is the sum and product of
two with itself:
+
=
=
x
, the only number
such that
+
=
=
x
, which also makes four the smallest squared
prime number . In
Knuth's up-arrow notation, , and so forth, for any number of up arrows. By consequence, four is the only square one more than a prime number, specifically
three. The sum of the first four prime numbers
two +
three +
five +
seven
7 is a number, numeral, and glyph.
7 or seven may also refer to:
* AD 7, the seventh year of the AD era
* 7 BC, the seventh year before the AD era
* The month of
July
Music Artists
* Seven (Swiss singer) (born 1978), a Swiss recording artist ...
is the only sum of four consecutive prime numbers that yields an
odd prime number,
seventeen
Seventeen or 17 may refer to:
*17 (number), the natural number following 16 and preceding 18
* one of the years 17 BC, AD 17, 1917, 2017
Literature
Magazines
* ''Seventeen'' (American magazine), an American magazine
* ''Seventeen'' (Japanese m ...
, which is the fourth
super-prime
Super-prime numbers, also known as higher-order primes or prime-indexed primes (PIPs), are the subsequence of prime numbers that occupy prime-numbered positions within the sequence of all prime numbers.
The subsequence begins
:3, 5, 11, 17, 31, ...
. Four lies between the first prop