216978665 has 16 divisors (see below), whose sum is σ = 272094336. Its totient is φ = 165792000.

The previous prime is 216978653. The next prime is 216978679. The reversal of 216978665 is 566879612.

It is not a de Polignac number, because 216978665 - 2¹⁰ = 216977641 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 137330 + ... + 138900.

It is an arithmetic number, because the mean of its divisors is an integer number (17005896).

Almost surely, 2^216978665 is an apocalyptic number.

It is an amenable number.

216978665 is a deficient number, since it is larger than the sum of its proper divisors (55115671).

216978665 is a wasteful number, since it uses less digits than its factorization.

216978665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2800.

The product of its digits is 1088640, while the sum is 50.

The square root of 216978665 is about 14730.1956877701. The cubic root of 216978665 is about 600.9048061535.

The spelling of 216978665 in words is "two hundred sixteen million, nine hundred seventy-eight thousand, six hundred sixty-five".