22781 has 8 divisors (see below), whose sum is σ = 26400. Its totient is φ = 19440.

The previous prime is 22777. The next prime is 22783. The reversal of 22781 is 18722.

Adding to 22781 its sum of digits (20), we get a square (22801 = 151^{2}).

Adding to 22781 its product of digits (224), we get a triangular number (23005 = T_{214}).

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 22781 - 2^{2} = 22777 is a prime.

It is a super-2 number, since 2×22781^{2} = 1037947922, which contains 22 as substring.

It is a plaindrome in base 12.

It is a nialpdrome in base 14.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (22783) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 155 + ... + 263.

It is an arithmetic number, because the mean of its divisors is an integer number (3300).

2^{22781} is an apocalyptic number.

22781 is the 68-th centered decagonal number.

It is an amenable number.

22781 is a deficient number, since it is larger than the sum of its proper divisors (3619).

22781 is a wasteful number, since it uses less digits than its factorization.

22781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 139.

The product of its digits is 224, while the sum is 20.

The square root of 22781 is about 150.9337603056. The cubic root of 22781 is about 28.3481199250.

The spelling of 22781 in words is "twenty-two thousand, seven hundred eighty-one".

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