2161646865 has 64 divisors (see below), whose sum is σ = 4406814720. Its totient is φ = 984830400.

The previous prime is 2161646857. The next prime is 2161646909. The reversal of 2161646865 is 5686461612.

2161646865 is a `hidden beast` number, since 21 + 616 + 4 + 6 + 8 + 6 + 5 = 666.

It is not a de Polignac number, because 2161646865 - 2³ = 2161646857 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a self number, because there is not a number n which added to its sum of digits gives 2161646865.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 286390 + ... + 293840.

It is an arithmetic number, because the mean of its divisors is an integer number (68856480).

Almost surely, 2^2161646865 is an apocalyptic number.

It is an amenable number.

2161646865 is an abundant number, since it is smaller than the sum of its proper divisors (2245167855).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

2161646865 is a wasteful number, since it uses less digits than its factorization.

2161646865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7779 (or 7773 counting only the distinct ones).

The product of its digits is 414720, while the sum is 45.

The square root of 2161646865 is about 46493.5142251046. The cubic root of 2161646865 is about 1292.9892549212.

The spelling of 2161646865 in words is "two billion, one hundred sixty-one million, six hundred forty-six thousand, eight hundred sixty-five".