18689686446649 has 9 divisors (see below), whose sum is σ = 19049209076653. Its totient is φ = 18336826049152.

The previous prime is 18689686446601. The next prime is 18689686446659. The reversal of 18689686446649 is 94664468698681.

The square root of 18689686446649 is 4323157.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 4 ways, for example, as 3146632515625 + 15543053931024 = 1773875^2 + 3942468^2 .

It is not a de Polignac number, because 18689686446649 - 2⁷ = 18689686446521 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18689686446659) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 229086537 + ... + 229168105.

Almost surely, 2^{18689686446649} is an apocalyptic number.

18689686446649 is the 4323157-th square number.

18689686446649 is the 2161579-th centered octagonal number.

It is an amenable number.

18689686446649 is a deficient number, since it is larger than the sum of its proper divisors (359522630004).

18689686446649 is an frugal number, since it uses more digits than its factorization.

18689686446649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 163244 (or 81622 counting only the distinct ones).

The product of its digits is 20639121408, while the sum is 85.

The spelling of 18689686446649 in words is "eighteen trillion, six hundred eighty-nine billion, six hundred eighty-six million, four hundred forty-six thousand, six hundred forty-nine".