206810021 has 16 divisors (see below), whose sum is σ = 235726848. Its totient is φ = 179727600.

The previous prime is 206809963. The next prime is 206810029. The reversal of 206810021 is 120018602.

It is a cyclic number.

It is not a de Polignac number, because 206810021 - 2⁶ = 206809957 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 206809975 and 206810002.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (206810029) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 24650 + ... + 31956.

It is an arithmetic number, because the mean of its divisors is an integer number (14732928).

Almost surely, 2^206810021 is an apocalyptic number.

It is an amenable number.

206810021 is a deficient number, since it is larger than the sum of its proper divisors (28916827).

206810021 is a wasteful number, since it uses less digits than its factorization.

206810021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7432.

The product of its (nonzero) digits is 192, while the sum is 20.

The square root of 206810021 is about 14380.8908277617. The cubic root of 206810021 is about 591.3671456100.

Adding to 206810021 its reverse (120018602), we get a palindrome (326828623).

The spelling of 206810021 in words is "two hundred six million, eight hundred ten thousand, twenty-one".