2102809 has 2 divisors, whose sum is σ = 2102810. Its totient is φ = 2102808.

The previous prime is 2102801. The next prime is 2102831. The reversal of 2102809 is 9082012.

It is an a-pointer prime, because the next prime (2102831) can be obtained adding 2102809 to its sum of digits (22).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1651225 + 451584 = 1285^2 + 672^2 .

It is a cyclic number.

It is not a de Polignac number, because 2102809 - 2³ = 2102801 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 2102809.

It is not a weakly prime, because it can be changed into another prime (2102801) 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, 1051404 + 1051405.

It is an arithmetic number, because the mean of its divisors is an integer number (1051405).

2^2102809 is an apocalyptic number.

It is an amenable number.

2102809 is a deficient number, since it is larger than the sum of its proper divisors (1).

2102809 is an equidigital number, since it uses as much as digits as its factorization.

2102809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 288, while the sum is 22.

The square root of 2102809 is about 1450.1065478095. The cubic root of 2102809 is about 128.1149886288.

The spelling of 2102809 in words is "two million, one hundred two thousand, eight hundred nine".