216405809 has 8 divisors (see below), whose sum is σ = 218979360. Its totient is φ = 213847776.

The previous prime is 216405803. The next prime is 216405811. The reversal of 216405809 is 908504612.

216405809 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 216405809 - 2²⁴ = 199628593 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (216405803) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 25469 + ... + 32885.

It is an arithmetic number, because the mean of its divisors is an integer number (27372420).

Almost surely, 2^216405809 is an apocalyptic number.

It is an amenable number.

216405809 is a deficient number, since it is larger than the sum of its proper divisors (2573551).

216405809 is a wasteful number, since it uses less digits than its factorization.

216405809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7759.

The product of its (nonzero) digits is 17280, while the sum is 35.

The square root of 216405809 is about 14710.7378808814. The cubic root of 216405809 is about 600.3755140071.

The spelling of 216405809 in words is "two hundred sixteen million, four hundred five thousand, eight hundred nine".