1801809 has 6 divisors (see below), whose sum is σ = 2602626. Its totient is φ = 1201200.

The previous prime is 1801781. The next prime is 1801817. The reversal of 1801809 is 9081081.

It can be written as a sum of positive squares in only one way, i.e., 1096209 + 705600 = 1047^2 + 840^2 .

It is not a de Polignac number, because 1801809 - 2⁵ = 1801777 is a prime.

It is a Curzon number.

1801809 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (1801819) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 100092 + ... + 100109.

It is an arithmetic number, because the mean of its divisors is an integer number (433771).

2^1801809 is an apocalyptic number.

It is an amenable number.

1801809 is a deficient number, since it is larger than the sum of its proper divisors (800817).

1801809 is a wasteful number, since it uses less digits than its factorization.

1801809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 200207 (or 200204 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 27.

The square root of 1801809 is about 1342.3147916938. The cubic root of 1801809 is about 121.6847770210.

The spelling of 1801809 in words is "one million, eight hundred one thousand, eight hundred nine".