261365856 has 24 divisors (see below), whose sum is σ = 686085624. Its totient is φ = 87121920.

The previous prime is 261365851. The next prime is 261365869. The reversal of 261365856 is 658563162.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (24).

It is a super-2 number, since 2×261365856² = 136624221365225472, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261365851) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1361185 + ... + 1361376.

It is an arithmetic number, because the mean of its divisors is an integer number (28586901).

Almost surely, 2^261365856 is an apocalyptic number.

It is an amenable number.

261365856 is an abundant number, since it is smaller than the sum of its proper divisors (424719768).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

261365856 is a wasteful number, since it uses less digits than its factorization.

261365856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2722574 (or 2722566 counting only the distinct ones).

The product of its digits is 259200, while the sum is 42.

The square root of 261365856 is about 16166.8134151415. The cubic root of 261365856 is about 639.3661171748.

The spelling of 261365856 in words is "two hundred sixty-one million, three hundred sixty-five thousand, eight hundred fifty-six".