216561864 has 32 divisors (see below), whose sum is σ = 545545440. Its totient is φ = 71635200.

The previous prime is 216561833. The next prime is 216561871. The reversal of 216561864 is 468165612.

It is a happy number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 31297 + ... + 37584.

It is an arithmetic number, because the mean of its divisors is an integer number (17048295).

Almost surely, 2^216561864 is an apocalyptic number.

216561864 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

216561864 is an abundant number, since it is smaller than the sum of its proper divisors (328983576).

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

216561864 is a wasteful number, since it uses less digits than its factorization.

216561864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 69021 (or 69017 counting only the distinct ones).

The product of its digits is 69120, while the sum is 39.

The square root of 216561864 is about 14716.0410437047. The cubic root of 216561864 is about 600.5197940047.

The spelling of 216561864 in words is "two hundred sixteen million, five hundred sixty-one thousand, eight hundred sixty-four".