216409 has 4 divisors (see below), whose sum is σ = 217360. Its totient is φ = 215460.

The previous prime is 216401. The next prime is 216421. The reversal of 216409 is 904612.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 216409 - 2³ = 216401 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 216409.

It is not an unprimeable number, because it can be changed into a prime (216401) 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, 94 + ... + 664.

It is an arithmetic number, because the mean of its divisors is an integer number (54340).

2²¹⁶⁴⁰⁹ is an apocalyptic number.

It is an amenable number.

216409 is a deficient number, since it is larger than the sum of its proper divisors (951).

216409 is an equidigital number, since it uses as much as digits as its factorization.

216409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 950.

The product of its (nonzero) digits is 432, while the sum is 22.

The square root of 216409 is about 465.1978073895. The cubic root of 216409 is about 60.0378464927.

It can be divided in two parts, 216 and 409, that added together give a 4-th power (625 = 5⁴).

The spelling of 216409 in words is "two hundred sixteen thousand, four hundred nine".