1821009 has 4 divisors (see below), whose sum is σ = 2428016. Its totient is φ = 1214004.

The previous prime is 1820999. The next prime is 1821013. The reversal of 1821009 is 9001281.

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 1821009 - 2⁵ = 1820977 is a prime.

It is a D-number.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1821019) 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 in 3 ways as a sum of consecutive naturals, for example, 303499 + ... + 303504.

It is an arithmetic number, because the mean of its divisors is an integer number (607004).

2^1821009 is an apocalyptic number.

It is an amenable number.

1821009 is a deficient number, since it is larger than the sum of its proper divisors (607007).

1821009 is an equidigital number, since it uses as much as digits as its factorization.

1821009 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 607006.

The product of its (nonzero) digits is 144, while the sum is 21.

The square root of 1821009 is about 1349.4476647873. The cubic root of 1821009 is about 122.1154733982.

The spelling of 1821009 in words is "one million, eight hundred twenty-one thousand, nine".