23509 has 2 divisors, whose sum is σ = 23510. Its totient is φ = 23508.

The previous prime is 23497. The next prime is 23531. The reversal of 23509 is 90532.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 23409 + 100 = 153^2 + 10^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-23509 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (23539) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 11754 + 11755.

It is an arithmetic number, because the mean of its divisors is an integer number (11755).

2²³⁵⁰⁹ is an apocalyptic number.

It is an amenable number.

23509 is a deficient number, since it is larger than the sum of its proper divisors (1).

23509 is an equidigital number, since it uses as much as digits as its factorization.

23509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 270, while the sum is 19.

The square root of 23509 is about 153.3264491208. The cubic root of 23509 is about 28.6469277011.

The spelling of 23509 in words is "twenty-three thousand, five hundred nine".