16816591665 has 12 divisors (see below), whose sum is σ = 29148758964. Its totient is φ = 8968848864.

The previous prime is 16816591633. The next prime is 16816591679. The reversal of 16816591665 is 56619561861.

It can be written as a sum of positive squares in 2 ways, for example, as 4179234609 + 12637357056 = 64647^2 + 112416^2 .

It is not a de Polignac number, because 16816591665 - 2⁵ = 16816591633 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 186850974 + ... + 186851063.

It is an arithmetic number, because the mean of its divisors is an integer number (2429063247).

Almost surely, 2^16816591665 is an apocalyptic number.

16816591665 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

16816591665 is a deficient number, since it is larger than the sum of its proper divisors (12332167299).

16816591665 is a wasteful number, since it uses less digits than its factorization.

16816591665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 373702048 (or 373702045 counting only the distinct ones).

The product of its digits is 2332800, while the sum is 54.

The spelling of 16816591665 in words is "sixteen billion, eight hundred sixteen million, five hundred ninety-one thousand, six hundred sixty-five".