• 16 can be written using four 4's:

• There are 16 tetrasticks:

16 has 5 divisors (see below), whose sum is σ = 31. Its totient is φ = 8.

The previous prime is 13. The next prime is 17. The reversal of 16 is 61.

16 = T_{3} + T_{4}.

The square root of 16 is 4.

It is a perfect power (a square, a biquadrate), and thus also a powerful number.

It is a Jordan-Polya number, since it can be written as (2!)^{4}.

16 is nontrivially palindromic in base 3, base 7 and base 15.

16 is an esthetic number in base 3, base 14 and base 16, because in such bases its adjacent digits differ by 1.

16 is an idoneal number.

It is a magnanimous number.

It is an Ulam number.

It is an alternating number because its digits alternate between odd and even.

It is a pancake number, because a pancake can be divided into 16 parts by 5 straight cuts.

It is a Duffinian number.

16 is an undulating number in base 3.

Its product of digits (6) is a multiple of the sum of its prime divisors (2).

16 is a nontrivial repdigit in base 7 and base 15.

It is a plaindrome in base 6, base 7, base 9, base 10, base 11, base 12, base 13, base 14 and base 15.

It is a nialpdrome in base 2, base 4, base 5, base 7, base 8, base 15 and base 16.

It is a zygodrome in base 7 and base 15.

A polygon with 16 sides can be constructed with ruler and compass.

It is an impolite number, since it cannot be written as a nontrivial sum of consecutive naturals.

16 is the 4-th square number.

16 is the 3-rd centered pentagonal number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 16

16 is a deficient number, since it is larger than the sum of its proper divisors (15).

16 is an equidigital number, since it uses as much as digits as its factorization.

With its predecessor (15) it forms a Ruth-Aaron pair, since the sum of their prime factors is the same (8).

16 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8 (or 2 counting only the distinct ones).

The product of its digits is 6, while the sum is 7.

The cubic root of 16 is about 2.5198420998.

Adding to 16 its reverse (61), we get a palindrome (77).

Subtracting 16 from its reverse (61), we obtain a triangular number (45 = T_{9}).

The spelling of 16 in words is "sixteen", and thus it is an aban number, an oban number, and an uban number.

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