18687559513921 has 3 divisors (see below), whose sum is σ = 18687563836833. Its totient is φ = 18687555191010.

The previous prime is 18687559513871. The next prime is 18687559513927. The reversal of 18687559513921 is 12931595578681.

The square root of 18687559513921 is 4322911.

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 is not a de Polignac number, because 18687559513921 - 2⁷ = 18687559513793 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18687559513927) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 2161456 + ... + 6484366.

It is an arithmetic number, because the mean of its divisors is an integer number (6229187945611).

Almost surely, 2^{18687559513921} is an apocalyptic number.

18687559513921 is the 4322911-st square number.

18687559513921 is the 2161456-th centered octagonal number.

It is an amenable number.

18687559513921 is a deficient number, since it is larger than the sum of its proper divisors (4322912).

18687559513921 is an frugal number, since it uses more digits than its factorization.

18687559513921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8645822 (or 4322911 counting only the distinct ones).

The product of its digits is 163296000, while the sum is 70.

The spelling of 18687559513921 in words is "eighteen trillion, six hundred eighty-seven billion, five hundred fifty-nine million, five hundred thirteen thousand, nine hundred twenty-one".