213856633665 has 24 divisors (see below), whose sum is σ = 371301658728. Its totient is φ = 113867078400.

The previous prime is 213856633657. The next prime is 213856633667. The reversal of 213856633665 is 566336658312.

213856633665 is a `hidden beast` number, since 2 + 13 + 8 + 566 + 3 + 3 + 6 + 65 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 35807235984 + 178049397681 = 189228^2 + 421959^2 .

It is not a de Polignac number, because 213856633665 - 2³ = 213856633657 is a prime.

It is a super-2 number, since 2×213856633665² (a number of 23 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (213856633667) 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 23 ways as a sum of consecutive naturals, for example, 3926674 + ... + 3980763.

It is an arithmetic number, because the mean of its divisors is an integer number (15470902447).

Almost surely, 2^213856633665 is an apocalyptic number.

It is an amenable number.

213856633665 is a deficient number, since it is larger than the sum of its proper divisors (157445025063).

213856633665 is a wasteful number, since it uses less digits than its factorization.

213856633665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7908049 (or 7908046 counting only the distinct ones).

The product of its digits is 13996800, while the sum is 54.

The spelling of 213856633665 in words is "two hundred thirteen billion, eight hundred fifty-six million, six hundred thirty-three thousand, six hundred sixty-five".