2021209 has 4 divisors (see below), whose sum is σ = 2024116. Its totient is φ = 2018304.

The previous prime is 2021203. The next prime is 2021219. The reversal of 2021209 is 9021202.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 9021202 = 2 ⋅4510601.

It can be written as a sum of positive squares in 2 ways, for example, as 705600 + 1315609 = 840^2 + 1147^2 .

It is a cyclic number.

It is not a de Polignac number, because 2021209 - 2⁷ = 2021081 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 2021192 and 2021201.

It is not an unprimeable number, because it can be changed into a prime (2021203) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 277 + ... + 2029.

It is an arithmetic number, because the mean of its divisors is an integer number (506029).

2^2021209 is an apocalyptic number.

It is an amenable number.

2021209 is a deficient number, since it is larger than the sum of its proper divisors (2907).

2021209 is a wasteful number, since it uses less digits than its factorization.

2021209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2906.

The product of its (nonzero) digits is 72, while the sum is 16.

The square root of 2021209 is about 1421.6923014492. The cubic root of 2021209 is about 126.4359010143.

The spelling of 2021209 in words is "two million, twenty-one thousand, two hundred nine".