210409 has 4 divisors (see below), whose sum is σ = 222804. Its totient is φ = 198016.

The previous prime is 210407. The next prime is 210421. The reversal of 210409 is 904012.

210409 is nontrivially palindromic in base 15.

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

It can be written as a sum of positive squares in 2 ways, for example, as 90000 + 120409 = 300^2 + 347^2 .

It is not a de Polignac number, because 210409 - 2¹ = 210407 is a prime.

It is a Duffinian number.

210409 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 210392 and 210401.

It is not an unprimeable number, because it can be changed into a prime (210401) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6172 + ... + 6205.

It is an arithmetic number, because the mean of its divisors is an integer number (55701).

2²¹⁰⁴⁰⁹ is an apocalyptic number.

It is an amenable number.

210409 is a deficient number, since it is larger than the sum of its proper divisors (12395).

210409 is a wasteful number, since it uses less digits than its factorization.

210409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12394.

The product of its (nonzero) digits is 72, while the sum is 16.

The square root of 210409 is about 458.7036080085. The cubic root of 210409 is about 59.4777828216.

The spelling of 210409 in words is "two hundred ten thousand, four hundred nine".