2021309 has 6 divisors (see below), whose sum is σ = 2113566. Its totient is φ = 1932920.

The previous prime is 2021291. The next prime is 2021321. The reversal of 2021309 is 9031202.

It can be written as a sum of positive squares in only one way, i.e., 1968409 + 52900 = 1403^2 + 230^2 .

It is not a de Polignac number, because 2021309 - 2⁸ = 2021053 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2021339) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1382 + ... + 2439.

It is an arithmetic number, because the mean of its divisors is an integer number (352261).

2^2021309 is an apocalyptic number.

It is an amenable number.

2021309 is a deficient number, since it is larger than the sum of its proper divisors (92257).

2021309 is an equidigital number, since it uses as much as digits as its factorization.

2021309 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3867 (or 3844 counting only the distinct ones).

The product of its (nonzero) digits is 108, while the sum is 17.

The square root of 2021309 is about 1421.7274703684. The cubic root of 2021309 is about 126.4379861329.

The spelling of 2021309 in words is "two million, twenty-one thousand, three hundred nine".