218211991665 has 32 divisors (see below), whose sum is σ = 355000195200. Its totient is φ = 114427537920.

The previous prime is 218211991609. The next prime is 218211991681. The reversal of 218211991665 is 566199112812.

It is not a de Polignac number, because 218211991665 - 2¹⁴ = 218211975281 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2388141 + ... + 2477829.

It is an arithmetic number, because the mean of its divisors is an integer number (11093756100).

Almost surely, 2^218211991665 is an apocalyptic number.

It is an amenable number.

218211991665 is a deficient number, since it is larger than the sum of its proper divisors (136788203535).

218211991665 is a wasteful number, since it uses less digits than its factorization.

218211991665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 92417.

The product of its digits is 466560, while the sum is 51.

The spelling of 218211991665 in words is "two hundred eighteen billion, two hundred eleven million, nine hundred ninety-one thousand, six hundred sixty-five".