23561 has 2 divisors, whose sum is σ = 23562. Its totient is φ = 23560.

The previous prime is 23557. The next prime is 23563. The reversal of 23561 is 16532.

23561 is nontrivially palindromic in base 5.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17161 + 6400 = 131^2 + 80^2 .

It is a cyclic number.

It is not a de Polignac number, because 23561 - 2² = 23557 is a prime.

It is a Sophie Germain prime.

Together with 23563, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a plaindrome in base 11.

It is a nialpdrome in base 13.

It is not a weakly prime, because it can be changed into another prime (23563) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 11780 + 11781.

It is an arithmetic number, because the mean of its divisors is an integer number (11781).

2²³⁵⁶¹ is an apocalyptic number.

It is an amenable number.

23561 is a deficient number, since it is larger than the sum of its proper divisors (1).

23561 is an equidigital number, since it uses as much as digits as its factorization.

23561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 180, while the sum is 17.

The square root of 23561 is about 153.4959282848. The cubic root of 23561 is about 28.6680337068.

The spelling of 23561 in words is "twenty-three thousand, five hundred sixty-one".