18487944657121 has 3 divisors (see below), whose sum is σ = 18487948956883. Its totient is φ = 18487940357360.

The previous prime is 18487944657109. The next prime is 18487944657131. The reversal of 18487944657121 is 12175644978481.

The square root of 18487944657121 is 4299761.

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

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 672792017121 + 17815152640000 = 820239^2 + 4220800^2 .

It is not a de Polignac number, because 18487944657121 - 2²⁹ = 18487407786209 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18487944657131) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 2149881 + ... + 6449641.

Almost surely, 2^{18487944657121} is an apocalyptic number.

18487944657121 is the 4299761-st square number.

18487944657121 is the 2149881-st centered octagonal number.

It is an amenable number.

18487944657121 is a deficient number, since it is larger than the sum of its proper divisors (4299762).

18487944657121 is an frugal number, since it uses more digits than its factorization.

18487944657121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8599522 (or 4299761 counting only the distinct ones).

The product of its digits is 108380160, while the sum is 67.

The spelling of 18487944657121 in words is "eighteen trillion, four hundred eighty-seven billion, nine hundred forty-four million, six hundred fifty-seven thousand, one hundred twenty-one".