20816409 has 4 divisors (see below), whose sum is σ = 27755216. Its totient is φ = 13877604.

The previous prime is 20816387. The next prime is 20816413. The reversal of 20816409 is 90461802.

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.

It is not a de Polignac number, because 20816409 - 2⁷ = 20816281 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20816489) 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, 3469399 + ... + 3469404.

It is an arithmetic number, because the mean of its divisors is an integer number (6938804).

Almost surely, 2^20816409 is an apocalyptic number.

It is an amenable number.

20816409 is a deficient number, since it is larger than the sum of its proper divisors (6938807).

20816409 is an equidigital number, since it uses as much as digits as its factorization.

20816409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6938806.

The product of its (nonzero) digits is 3456, while the sum is 30.

The square root of 20816409 is about 4562.5003013699. The cubic root of 20816409 is about 275.0860733322.

The spelling of 20816409 in words is "twenty million, eight hundred sixteen thousand, four hundred nine".