2123809 has 4 divisors (see below), whose sum is σ = 2127040. Its totient is φ = 2120580.

The previous prime is 2123791. The next prime is 2123831. The reversal of 2123809 is 9083212.

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 2123809 - 2⁵ = 2123777 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2123879) 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, 237 + ... + 2074.

It is an arithmetic number, because the mean of its divisors is an integer number (531760).

2^2123809 is an apocalyptic number.

It is an amenable number.

2123809 is a deficient number, since it is larger than the sum of its proper divisors (3231).

2123809 is an equidigital number, since it uses as much as digits as its factorization.

2123809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3230.

The product of its (nonzero) digits is 864, while the sum is 25.

The square root of 2123809 is about 1457.3294068261. The cubic root of 2123809 is about 128.5400562491.

The spelling of 2123809 in words is "two million, one hundred twenty-three thousand, eight hundred nine".