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11

11 is a natural number that follows 10 and precedes 12. In decimal notation used in everyday counting, it is the smallest two-digit prime and the fifth prime number overall. The two digits are identical, so 11 is a repunit of length two in base 10.

In mathematics, 11 is prime; its only positive divisors are 1 and 11. It pairs with 13

In science, the element with atomic number 11 is sodium (Na). Sodium is a soft, highly reactive

In culture and everyday life, 11 has various associations. In sports, football (soccer) teams field 11 players.

In other bases, 11 decimal appears as 1011 in binary, 13 in octal, and B in hexadecimal.

as
a
twin
prime.
In
positional
numeral
systems,
its
representations
include
1011
in
binary,
13
in
octal,
and
B
in
hexadecimal.
In
Roman
numerals,
11
is
XI.
alkali
metal;
it
is
essential
for
biological
processes
and
is
a
common
component
of
table
salt
(sodium
chloride).
The
month
of
November
is
the
eleventh
month
of
the
year.
Dates
such
as
11/11
are
observed
as
Remembrance
or
Armistice
Day
in
many
countries.
The
number
also
appears
in
various
mathematical
contexts
as
a
representative
example
of
prime
behavior,
palindromic
digits
in
base
10,
and
as
a
point
of
reference
in
calendar
and
sports
traditions.