209409 has 12 divisors (see below), whose sum is σ = 292656. Its totient is φ = 133168.

The previous prime is 209401. The next prime is 209431. The reversal of 209409 is 904902.

It is not a de Polignac number, because 209409 - 2³ = 209401 is a prime.

It is an Ulam number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (209401) 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, 2482 + ... + 2564.

It is an arithmetic number, because the mean of its divisors is an integer number (24388).

It is a Proth number, since it is equal to 409 ⋅ 2⁹ + 1 and 409 < 2⁹.

2²⁰⁹⁴⁰⁹ is an apocalyptic number.

209409 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

209409 is a deficient number, since it is larger than the sum of its proper divisors (83247).

209409 is an equidigital number, since it uses as much as digits as its factorization.

209409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 144 (or 115 counting only the distinct ones).

The product of its (nonzero) digits is 648, while the sum is 24.

The square root of 209409 is about 457.6122813037. The cubic root of 209409 is about 59.3834074890.

The spelling of 209409 in words is "two hundred nine thousand, four hundred nine".