18778866904681 has 27 divisors (see below), whose sum is σ = 21013578654597. Its totient is φ = 16773606420480.

The previous prime is 18778866904673. The next prime is 18778866904717. The reversal of 18778866904681 is 18640966887781.

The square root of 18778866904681 is 4333459.

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 493493605081 + 18285373299600 = 702491^2 + 4276140^2 .

It is not a de Polignac number, because 18778866904681 - 2³ = 18778866904673 is a prime.

It is a super-2 number, since 2×18778866904681² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18778866904481) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 1746378601 + ... + 1746389353.

It is an arithmetic number, because the mean of its divisors is an integer number (778280690911).

Almost surely, 2^{18778866904681} is an apocalyptic number.

18778866904681 is the 4333459-th square number.

18778866904681 is the 2166730-th centered octagonal number.

It is an amenable number.

18778866904681 is a deficient number, since it is larger than the sum of its proper divisors (2234711749916).

18778866904681 is an frugal number, since it uses more digits than its factorization.

18778866904681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21594 (or 10797 counting only the distinct ones).

The product of its (nonzero) digits is 1560674304, while the sum is 79.

The spelling of 18778866904681 in words is "eighteen trillion, seven hundred seventy-eight billion, eight hundred sixty-six million, nine hundred four thousand, six hundred eighty-one".