2165861 has 4 divisors (see below), whose sum is σ = 2170272. Its totient is φ = 2161452.

The previous prime is 2165857. The next prime is 2165873. The reversal of 2165861 is 1685612.

It is a happy number.

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 2165861 - 2² = 2165857 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 (2165461) 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, 1361 + ... + 2486.

It is an arithmetic number, because the mean of its divisors is an integer number (542568).

2^2165861 is an apocalyptic number.

It is an amenable number.

2165861 is a deficient number, since it is larger than the sum of its proper divisors (4411).

2165861 is an equidigital number, since it uses as much as digits as its factorization.

2165861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4410.

The product of its digits is 2880, while the sum is 29.

The square root of 2165861 is about 1471.6864475832. The cubic root of 2165861 is about 129.3828937905.

Subtracting from 2165861 its reverse (1685612), we obtain a square (480249 = 693²).

The spelling of 2165861 in words is "two million, one hundred sixty-five thousand, eight hundred sixty-one".