1021809 has 12 divisors (see below), whose sum is σ = 1409936. Its totient is φ = 657888.

The previous prime is 1021807. The next prime is 1021831. The reversal of 1021809 is 9081201.

It is not a de Polignac number, because 1021809 - 2¹ = 1021807 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 16.

It is not an unprimeable number, because it can be changed into a prime (1021807) 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 11 ways as a sum of consecutive naturals, for example, 11437 + ... + 11525.

2^1021809 is an apocalyptic number.

It is an amenable number.

1021809 is a deficient number, since it is larger than the sum of its proper divisors (388127).

1021809 is an frugal number, since it uses more digits than its factorization.

1021809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 224 (or 135 counting only the distinct ones).

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

The square root of 1021809 is about 1010.8456855524. The cubic root of 1021809 is about 100.7217449763.

It can be divided in two parts, 1021 and 809, that added together give a triangular number (1830 = T₆₀).

The spelling of 1021809 in words is "one million, twenty-one thousand, eight hundred nine".