209491 has 4 divisors (see below), whose sum is σ = 221832. Its totient is φ = 197152.

The previous prime is 209477. The next prime is 209497. The reversal of 209491 is 194902.

209491 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 209491 - 2⁵ = 209459 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (209497) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6145 + ... + 6178.

It is an arithmetic number, because the mean of its divisors is an integer number (55458).

2²⁰⁹⁴⁹¹ is an apocalyptic number.

209491 is a deficient number, since it is larger than the sum of its proper divisors (12341).

209491 is a wasteful number, since it uses less digits than its factorization.

209491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12340.

The product of its (nonzero) digits is 648, while the sum is 25.

The square root of 209491 is about 457.7018680320. The cubic root of 209491 is about 59.3911575602.

The spelling of 209491 in words is "two hundred nine thousand, four hundred ninety-one".