2001809 has 2 divisors, whose sum is σ = 2001810. Its totient is φ = 2001808.

The previous prime is 2001799. The next prime is 2001833. The reversal of 2001809 is 9081002.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1329409 + 672400 = 1153^2 + 820^2 .

It is a cyclic number.

It is not a de Polignac number, because 2001809 - 2⁴ = 2001793 is a prime.

It is not a weakly prime, because it can be changed into another prime (2001409) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1000904 + 1000905.

It is an arithmetic number, because the mean of its divisors is an integer number (1000905).

2^2001809 is an apocalyptic number.

It is an amenable number.

2001809 is a deficient number, since it is larger than the sum of its proper divisors (1).

2001809 is an equidigital number, since it uses as much as digits as its factorization.

2001809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 144, while the sum is 20.

The square root of 2001809 is about 1414.8529958975. The cubic root of 2001809 is about 126.0300801619.

The spelling of 2001809 in words is "two million, one thousand, eight hundred nine".