18978561 has 12 divisors (see below), whose sum is σ = 31329792. Its totient is φ = 10844856.

The previous prime is 18978559. The next prime is 18978569. The reversal of 18978561 is 16587981.

18978561 is a `hidden beast` number, since 1 + 89 + 7 + 8 + 561 = 666.

It is not a de Polignac number, because 18978561 - 2¹ = 18978559 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (18978569) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 150561 + ... + 150686.

It is an arithmetic number, because the mean of its divisors is an integer number (2610816).

Almost surely, 2^18978561 is an apocalyptic number.

It is an amenable number.

18978561 is a deficient number, since it is larger than the sum of its proper divisors (12351231).

18978561 is a wasteful number, since it uses less digits than its factorization.

18978561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 301260 (or 301257 counting only the distinct ones).

The product of its digits is 120960, while the sum is 45.

The square root of 18978561 is about 4356.4390274627. The cubic root of 18978561 is about 266.7397624272.

The spelling of 18978561 in words is "eighteen million, nine hundred seventy-eight thousand, five hundred sixty-one".