18978689 has 4 divisors (see below), whose sum is σ = 19146756. Its totient is φ = 18810624.

The previous prime is 18978683. The next prime is 18978691. The reversal of 18978689 is 98687981.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 8526400 + 10452289 = 2920^2 + 3233^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18978689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18978683) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 83864 + ... + 84089.

It is an arithmetic number, because the mean of its divisors is an integer number (4786689).

Almost surely, 2^18978689 is an apocalyptic number.

It is an amenable number.

18978689 is a deficient number, since it is larger than the sum of its proper divisors (168067).

18978689 is a wasteful number, since it uses less digits than its factorization.

18978689 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 168066.

The product of its digits is 1741824, while the sum is 56.

The square root of 18978689 is about 4356.4537183356. The cubic root of 18978689 is about 266.7403620971.

The spelling of 18978689 in words is "eighteen million, nine hundred seventy-eight thousand, six hundred eighty-nine".