216505818 has 32 divisors (see below), whose sum is σ = 481662720. Its totient is φ = 72087840.

The previous prime is 216505811. The next prime is 216505819. The reversal of 216505818 is 818505612.

216505818 is a `hidden beast` number, since 21 + 6 + 50 + 581 + 8 = 666.

It is an alternating number because its digits alternate between even and odd.

It is not an unprimeable number, because it can be changed into a prime (216505811) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 64846 + ... + 68102.

It is an arithmetic number, because the mean of its divisors is an integer number (15051960).

Almost surely, 2^216505818 is an apocalyptic number.

216505818 is an abundant number, since it is smaller than the sum of its proper divisors (265156902).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

216505818 is a wasteful number, since it uses less digits than its factorization.

216505818 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4499 (or 4493 counting only the distinct ones).

The product of its (nonzero) digits is 19200, while the sum is 36.

The square root of 216505818 is about 14714.1366719220. The cubic root of 216505818 is about 600.4679848887.

The spelling of 216505818 in words is "two hundred sixteen million, five hundred five thousand, eight hundred eighteen".