861895561 has 4 divisors (see below), whose sum is σ = 866710800. Its totient is φ = 857080324.

The previous prime is 861895553. The next prime is 861895579. The reversal of 861895561 is 165598168.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 861895561 - 2³ = 861895553 is a prime.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (861892561) 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 3 ways as a sum of consecutive naturals, for example, 2407351 + ... + 2407708.

It is an arithmetic number, because the mean of its divisors is an integer number (216677700).

Almost surely, 2^861895561 is an apocalyptic number.

It is an amenable number.

861895561 is a deficient number, since it is larger than the sum of its proper divisors (4815239).

861895561 is a wasteful number, since it uses less digits than its factorization.

861895561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4815238.

The product of its digits is 518400, while the sum is 49.

The square root of 861895561 is about 29358.0578547015. The cubic root of 861895561 is about 951.6667180849. Note that the first 3 decimals are identical.

The spelling of 861895561 in words is "eight hundred sixty-one million, eight hundred ninety-five thousand, five hundred sixty-one".