16531616665 has 4 divisors (see below), whose sum is σ = 19837940004. Its totient is φ = 13225293328.

The previous prime is 16531616627. The next prime is 16531616669. The reversal of 16531616665 is 56661613561.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 56661613561 = 7 ⋅8094516223.

It can be written as a sum of positive squares in 2 ways, for example, as 9551348361 + 6980268304 = 97731^2 + 83548^2 .

It is a cyclic number.

It is not a de Polignac number, because 16531616665 - 2⁷ = 16531616537 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16531616669) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1653161662 + ... + 1653161671.

It is an arithmetic number, because the mean of its divisors is an integer number (4959485001).

Almost surely, 2^16531616665 is an apocalyptic number.

It is an amenable number.

16531616665 is a deficient number, since it is larger than the sum of its proper divisors (3306323339).

16531616665 is an equidigital number, since it uses as much as digits as its factorization.

16531616665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3306323338.

The product of its digits is 583200, while the sum is 46.

The spelling of 16531616665 in words is "sixteen billion, five hundred thirty-one million, six hundred sixteen thousand, six hundred sixty-five".