209391 has 24 divisors (see below), whose sum is σ = 351360. Its totient is φ = 108576.

The previous prime is 209381. The next prime is 209393. The reversal of 209391 is 193902.

It is a happy number.

It is not a de Polignac number, because 209391 - 2⁵ = 209359 is a prime.

209391 is a lucky number.

It is a plaindrome in base 11.

It is a nialpdrome in base 13.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (209393) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3520 + ... + 3578.

It is an arithmetic number, because the mean of its divisors is an integer number (14640).

2²⁰⁹³⁹¹ is an apocalyptic number.

209391 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

209391 is a deficient number, since it is larger than the sum of its proper divisors (141969).

209391 is a wasteful number, since it uses less digits than its factorization.

209391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 95 (or 82 counting only the distinct ones).

The product of its (nonzero) digits is 486, while the sum is 24.

The square root of 209391 is about 457.5926135767. The cubic root of 209391 is about 59.3817059831.

The spelling of 209391 in words is "two hundred nine thousand, three hundred ninety-one".