261388865 has 4 divisors (see below), whose sum is σ = 313666644. Its totient is φ = 209111088.

The previous prime is 261388849. The next prime is 261388877. The reversal of 261388865 is 568883162.

261388865 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 76755121 + 184633744 = 8761^2 + 13588^2 .

It is a cyclic number.

It is not a de Polignac number, because 261388865 - 2⁴ = 261388849 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26138882 + ... + 26138891.

It is an arithmetic number, because the mean of its divisors is an integer number (78416661).

Almost surely, 2^261388865 is an apocalyptic number.

It is an amenable number.

261388865 is a deficient number, since it is larger than the sum of its proper divisors (52277779).

261388865 is an equidigital number, since it uses as much as digits as its factorization.

261388865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 52277778.

The product of its digits is 552960, while the sum is 47.

The square root of 261388865 is about 16167.5250115780. The cubic root of 261388865 is about 639.3848785432.

The spelling of 261388865 in words is "two hundred sixty-one million, three hundred eighty-eight thousand, eight hundred sixty-five".