2105809 has 2 divisors, whose sum is σ = 2105810. Its totient is φ = 2105808.

The previous prime is 2105767. The next prime is 2105813. The reversal of 2105809 is 9085012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1763584 + 342225 = 1328^2 + 585^2 .

It is a cyclic number.

It is not a de Polignac number, because 2105809 - 2⁷ = 2105681 is a prime.

It is not a weakly prime, because it can be changed into another prime (2105819) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1052904 + 1052905.

It is an arithmetic number, because the mean of its divisors is an integer number (1052905).

2^2105809 is an apocalyptic number.

It is an amenable number.

2105809 is a deficient number, since it is larger than the sum of its proper divisors (1).

2105809 is an equidigital number, since it uses as much as digits as its factorization.

2105809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 720, while the sum is 25.

The square root of 2105809 is about 1451.1405858841. The cubic root of 2105809 is about 128.1758853205.

The spelling of 2105809 in words is "two million, one hundred five thousand, eight hundred nine".