• 22 can be written using four 4's:

• Deleting all the even digits from 2^{22} = 4194304 we obtain a prime (193).

22 has 4 divisors (see below), whose sum is σ = 36. Its totient is φ = 10.

The previous prime is 19. The next prime is 23.

22 is nontrivially palindromic in base 10.

22 is an esthetic number in base 6, because in such base its adjacent digits differ by 1.

It is a semiprime because it is the product of two primes.

It is a Smith number, since the sum of its digits (4) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a nude number because it is divisible by every one of its digits.

22 is an idoneal number.

It is a pancake number, because a pancake can be divided into 22 parts by 6 straight cuts.

It is the 11-th Perrin number.

It is a partition number, being equal to the number of ways a set of 8 identical objects can be partitioned into subset.

22 is a nontrivial repdigit in base 10.

It is a plaindrome in base 4, base 6, base 8, base 9, base 10, base 12, base 13, base 14, base 15 and base 16.

It is a nialpdrome in base 3, base 5, base 7, base 10 and base 11.

It is a zygodrome in base 10.

It is a congruent number.

It is a pernicious number, because its binary representation contains a prime number (3) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4 + ... + 7.

It is an arithmetic number, because the mean of its divisors is an integer number (9).

It is a self-describing number.

22 is the 4-th pentagonal number.

22 is the 3-rd centered heptagonal number.

22 is a deficient number, since it is larger than the sum of its proper divisors (14).

22 is a wasteful number, since it uses less digits than its factorization.

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

The sum of its prime factors is 13.

The product of its digits is 4, while the sum is 4.

The square root of 22 is about 4.6904157598. The cubic root of 22 is about 2.8020393307.

The spelling of 22 in words is "twenty-two", and thus it is an aban number, an iban number, and an uban number.

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