216661665 has 32 divisors (see below), whose sum is σ = 381946752. Its totient is φ = 104000000.

The previous prime is 216661661. The next prime is 216661667. The reversal of 216661665 is 566166612.

It is not a de Polignac number, because 216661665 - 2² = 216661661 is a prime.

It is not an unprimeable number, because it can be changed into a prime (216661661) by changing a digit.

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 31 ways as a sum of consecutive naturals, for example, 10165 + ... + 23165.

It is an arithmetic number, because the mean of its divisors is an integer number (11935836).

Almost surely, 2^216661665 is an apocalyptic number.

It is an amenable number.

216661665 is a deficient number, since it is larger than the sum of its proper divisors (165285087).

216661665 is a wasteful number, since it uses less digits than its factorization.

216661665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13121.

The product of its digits is 77760, while the sum is 39.

The square root of 216661665 is about 14719.4315447303. The cubic root of 216661665 is about 600.6120282678.

The spelling of 216661665 in words is "two hundred sixteen million, six hundred sixty-one thousand, six hundred sixty-five".