865868561 has 4 divisors (see below), whose sum is σ = 889270452. Its totient is φ = 842466672.

The previous prime is 865868539. The next prime is 865868593. The reversal of 865868561 is 165868568.

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 577921600 + 287946961 = 24040^2 + 16969^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-865868561 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (865868761) 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, 11700890 + ... + 11700963.

It is an arithmetic number, because the mean of its divisors is an integer number (222317613).

Almost surely, 2^865868561 is an apocalyptic number.

It is an amenable number.

865868561 is a deficient number, since it is larger than the sum of its proper divisors (23401891).

865868561 is a wasteful number, since it uses less digits than its factorization.

865868561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23401890.

The product of its digits is 2764800, while the sum is 53.

The square root of 865868561 is about 29425.6446148593. The cubic root of 865868561 is about 953.1267469157.

The spelling of 865868561 in words is "eight hundred sixty-five million, eight hundred sixty-eight thousand, five hundred sixty-one".