206639 has 2 divisors, whose sum is σ = 206640. Its totient is φ = 206638.

The previous prime is 206627. The next prime is 206641. The reversal of 206639 is 936602.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 206639 - 2⁴ = 206623 is a prime.

Together with 206641, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (206699) 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, 103319 + 103320.

It is an arithmetic number, because the mean of its divisors is an integer number (103320).

2²⁰⁶⁶³⁹ is an apocalyptic number.

206639 is a deficient number, since it is larger than the sum of its proper divisors (1).

206639 is an equidigital number, since it uses as much as digits as its factorization.

206639 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1944, while the sum is 26.

The square root of 206639 is about 454.5756262714. The cubic root of 206639 is about 59.1204090823.

The spelling of 206639 in words is "two hundred six thousand, six hundred thirty-nine".