16409 has 4 divisors (see below), whose sum is σ = 16740. Its totient is φ = 16080.

The previous prime is 16381. The next prime is 16411. The reversal of 16409 is 90461.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 90461 = 7 ⋅12923.

It can be written as a sum of positive squares in 2 ways, for example, as 784 + 15625 = 28^2 + 125^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-16409 is a prime.

It is a Duffinian number.

It is a plaindrome in base 11 and base 15.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 16409.

It is not an unprimeable number, because it can be changed into a prime (12409) 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, 74 + ... + 195.

It is an arithmetic number, because the mean of its divisors is an integer number (4185).

2¹⁶⁴⁰⁹ is an apocalyptic number.

It is an amenable number.

16409 is a deficient number, since it is larger than the sum of its proper divisors (331).

16409 is an equidigital number, since it uses as much as digits as its factorization.

16409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 330.

The product of its (nonzero) digits is 216, while the sum is 20.

The square root of 16409 is about 128.0976190255. The cubic root of 16409 is about 25.4113285693.

The spelling of 16409 in words is "sixteen thousand, four hundred nine".