216815665 has 12 divisors (see below), whose sum is σ = 285982452. Its totient is φ = 157683680.

The previous prime is 216815623. The next prime is 216815681. The reversal of 216815665 is 566518612.

It can be written as a sum of positive squares in 2 ways, for example, as 147476736 + 69338929 = 12144^2 + 8327^2 .

It is not a de Polignac number, because 216815665 - 2¹⁹ = 216291377 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 (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 178582 + ... + 179791.

It is an arithmetic number, because the mean of its divisors is an integer number (23831871).

Almost surely, 2^216815665 is an apocalyptic number.

It is an amenable number.

216815665 is a deficient number, since it is larger than the sum of its proper divisors (69166787).

216815665 is a wasteful number, since it uses less digits than its factorization.

216815665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 358400 (or 358389 counting only the distinct ones).

The product of its digits is 86400, while the sum is 40.

The square root of 216815665 is about 14724.6617957765. The cubic root of 216815665 is about 600.7542967005.

The spelling of 216815665 in words is "two hundred sixteen million, eight hundred fifteen thousand, six hundred sixty-five".