865205661 has 16 divisors (see below), whose sum is σ = 1165328384. Its totient is φ = 570964464.

The previous prime is 865205659. The next prime is 865205729. The reversal of 865205661 is 166502568.

It is not a de Polignac number, because 865205661 - 2¹ = 865205659 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (865205161) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 183216 + ... + 187878.

It is an arithmetic number, because the mean of its divisors is an integer number (72833024).

Almost surely, 2^865205661 is an apocalyptic number.

It is an amenable number.

865205661 is a deficient number, since it is larger than the sum of its proper divisors (300122723).

865205661 is a wasteful number, since it uses less digits than its factorization.

865205661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5280.

The product of its (nonzero) digits is 86400, while the sum is 39.

The square root of 865205661 is about 29414.3784738009. The cubic root of 865205661 is about 952.8834501623.

The spelling of 865205661 in words is "eight hundred sixty-five million, two hundred five thousand, six hundred sixty-one".