2155809 has 4 divisors (see below), whose sum is σ = 2874416. Its totient is φ = 1437204.

The previous prime is 2155799. The next prime is 2155837. The reversal of 2155809 is 9085512.

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 not a de Polignac number, because 2155809 - 2⁴ = 2155793 is a prime.

It is a D-number.

It is a Duffinian number.

2155809 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (2155849) 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, 359299 + ... + 359304.

It is an arithmetic number, because the mean of its divisors is an integer number (718604).

2^2155809 is an apocalyptic number.

It is an amenable number.

2155809 is a deficient number, since it is larger than the sum of its proper divisors (718607).

2155809 is an equidigital number, since it uses as much as digits as its factorization.

2155809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 718606.

The product of its (nonzero) digits is 3600, while the sum is 30.

The square root of 2155809 is about 1468.2673462282. The cubic root of 2155809 is about 129.1824232368.

The spelling of 2155809 in words is "two million, one hundred fifty-five thousand, eight hundred nine".