206991 has 12 divisors (see below), whose sum is σ = 303160. Its totient is φ = 136080.

The previous prime is 206953. The next prime is 206993. The reversal of 206991 is 199602.

It is a happy number.

206991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 206991 - 2¹⁰ = 205967 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (206993) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 876 + ... + 1086.

2²⁰⁶⁹⁹¹ is an apocalyptic number.

206991 is a deficient number, since it is larger than the sum of its proper divisors (96169).

206991 is a wasteful number, since it uses less digits than its factorization.

206991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 326 (or 323 counting only the distinct ones).

The product of its (nonzero) digits is 972, while the sum is 27.

The square root of 206991 is about 454.9626358285. The cubic root of 206991 is about 59.1539596684.

The spelling of 206991 in words is "two hundred six thousand, nine hundred ninety-one".