209691 has 12 divisors (see below), whose sum is σ = 316368. Its totient is φ = 133584.

The previous prime is 209687. The next prime is 209701. The reversal of 209691 is 196902.

It is a happy number.

It is not a de Polignac number, because 209691 - 2² = 209687 is a prime.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 209691.

It is not an unprimeable number, because it can be changed into a prime (209621) 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, 300 + ... + 713.

It is an arithmetic number, because the mean of its divisors is an integer number (26364).

2²⁰⁹⁶⁹¹ is an apocalyptic number.

209691 is a deficient number, since it is larger than the sum of its proper divisors (106677).

209691 is a wasteful number, since it uses less digits than its factorization.

209691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1042 (or 1039 counting only the distinct ones).

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

The square root of 209691 is about 457.9202987420. The cubic root of 209691 is about 59.4100516949.

It can be divided in two parts, 2096 and 91, that added together give a 7-th power (2187 = 3⁷).

The spelling of 209691 in words is "two hundred nine thousand, six hundred ninety-one".