261026665 has 16 divisors (see below), whose sum is σ = 327444480. Its totient is φ = 199517760.

The previous prime is 261026639. The next prime is 261026669. The reversal of 261026665 is 566620162.

It is not a de Polignac number, because 261026665 - 2⁹ = 261026153 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 261026665.

It is not an unprimeable number, because it can be changed into a prime (261026669) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1587 + ... + 22903.

It is an arithmetic number, because the mean of its divisors is an integer number (20465280).

Almost surely, 2^261026665 is an apocalyptic number.

It is an amenable number.

261026665 is a deficient number, since it is larger than the sum of its proper divisors (66417815).

261026665 is a wasteful number, since it uses less digits than its factorization.

261026665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21432.

The product of its (nonzero) digits is 25920, while the sum is 34.

The square root of 261026665 is about 16156.3196613585. The cubic root of 261026665 is about 639.0894154947.

The spelling of 261026665 in words is "two hundred sixty-one million, twenty-six thousand, six hundred sixty-five".