206921857 has 2 divisors, whose sum is σ = 206921858. Its totient is φ = 206921856.

The previous prime is 206921849. The next prime is 206921861. The reversal of 206921857 is 758129602.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 192904321 + 14017536 = 13889^2 + 3744^2 .

It is a cyclic number.

It is not a de Polignac number, because 206921857 - 2³ = 206921849 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (206921867) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 103460928 + 103460929.

It is an arithmetic number, because the mean of its divisors is an integer number (103460929).

Almost surely, 2^206921857 is an apocalyptic number.

It is an amenable number.

206921857 is a deficient number, since it is larger than the sum of its proper divisors (1).

206921857 is an equidigital number, since it uses as much as digits as its factorization.

206921857 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 60480, while the sum is 40.

The square root of 206921857 is about 14384.7786566217. The cubic root of 206921857 is about 591.4737236471.

The spelling of 206921857 in words is "two hundred six million, nine hundred twenty-one thousand, eight hundred fifty-seven".