861918809 has 8 divisors (see below), whose sum is σ = 873585000. Its totient is φ = 850296832.

The previous prime is 861918803. The next prime is 861918821. The reversal of 861918809 is 908819168.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 672400 + 861246409 = 820^2 + 29347^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 861918809 - 2⁸ = 861918553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (861918803) 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 7 ways as a sum of consecutive naturals, for example, 29177 + ... + 50745.

It is an arithmetic number, because the mean of its divisors is an integer number (109198125).

Almost surely, 2^861918809 is an apocalyptic number.

861918809 is a gapful number since it is divisible by the number (89) formed by its first and last digit.

It is an amenable number.

861918809 is a deficient number, since it is larger than the sum of its proper divisors (11666191).

861918809 is a wasteful number, since it uses less digits than its factorization.

861918809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22107.

The product of its (nonzero) digits is 248832, while the sum is 50.

The square root of 861918809 is about 29358.4537910293. The cubic root of 861918809 is about 951.6752744769.

The spelling of 861918809 in words is "eight hundred sixty-one million, nine hundred eighteen thousand, eight hundred nine".