261857409 has 24 divisors (see below), whose sum is σ = 404621088. Its totient is φ = 149360640.

The previous prime is 261857389. The next prime is 261857413. The reversal of 261857409 is 904758162.

It is not a de Polignac number, because 261857409 - 2⁵ = 261857377 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261857459) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 4192 + ... + 23265.

It is an arithmetic number, because the mean of its divisors is an integer number (16859212).

Almost surely, 2^261857409 is an apocalyptic number.

It is an amenable number.

261857409 is a deficient number, since it is larger than the sum of its proper divisors (142763679).

261857409 is a wasteful number, since it uses less digits than its factorization.

261857409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27505 (or 27488 counting only the distinct ones).

The product of its (nonzero) digits is 120960, while the sum is 42.

The square root of 261857409 is about 16182.0088060784. The cubic root of 261857409 is about 639.7666866026.

The spelling of 261857409 in words is "two hundred sixty-one million, eight hundred fifty-seven thousand, four hundred nine".