206921861 has 2 divisors, whose sum is σ = 206921862. Its totient is φ = 206921860.

The previous prime is 206921857. The next prime is 206921867. The reversal of 206921861 is 168129602.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 201469636 + 5452225 = 14194^2 + 2335^2 .

It is a cyclic number.

It is not a de Polignac number, because 206921861 - 2² = 206921857 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (206921867) 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 as a sum of consecutive naturals, namely, 103460930 + 103460931.

It is an arithmetic number, because the mean of its divisors is an integer number (103460931).

Almost surely, 2^206921861 is an apocalyptic number.

It is an amenable number.

206921861 is a deficient number, since it is larger than the sum of its proper divisors (1).

206921861 is an equidigital number, since it uses as much as digits as its factorization.

206921861 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 10368, while the sum is 35.

The square root of 206921861 is about 14384.7787956576. The cubic root of 206921861 is about 591.4737274583.

The spelling of 206921861 in words is "two hundred six million, nine hundred twenty-one thousand, eight hundred sixty-one".