209091 has 4 divisors (see below), whose sum is σ = 278792. Its totient is φ = 139392.

The previous prime is 209089. The next prime is 209123. The reversal of 209091 is 190902.

It is a happy number.

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

It is not a de Polignac number, because 209091 - 2¹ = 209089 is a prime.

It is a D-number.

It is a Duffinian number.

It is a zygodrome in base 2.

It is not an unprimeable number, because it can be changed into a prime (209021) 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, 34846 + ... + 34851.

It is an arithmetic number, because the mean of its divisors is an integer number (69698).

2²⁰⁹⁰⁹¹ is an apocalyptic number.

209091 is a deficient number, since it is larger than the sum of its proper divisors (69701).

209091 is an equidigital number, since it uses as much as digits as its factorization.

209091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 69700.

The product of its (nonzero) digits is 162, while the sum is 21.

The square root of 209091 is about 457.2646935857. The cubic root of 209091 is about 59.3533331840.

Adding to 209091 its reverse (190902), we get a palindrome (399993).

It can be divided in two parts, 20909 and 1, that added together give a triangular number (20910 = T₂₀₄).

The spelling of 209091 in words is "two hundred nine thousand, ninety-one".