18978385 has 4 divisors (see below), whose sum is σ = 22774068. Its totient is φ = 15182704.

The previous prime is 18978329. The next prime is 18978403. The reversal of 18978385 is 58387981.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 58387981 = 397 ⋅147073.

It can be written as a sum of positive squares in 2 ways, for example, as 4870849 + 14107536 = 2207^2 + 3756^2 .

It is a cyclic number.

It is not a de Polignac number, because 18978385 - 2⁷ = 18978257 is a prime.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1897834 + ... + 1897843.

It is an arithmetic number, because the mean of its divisors is an integer number (5693517).

Almost surely, 2^18978385 is an apocalyptic number.

It is an amenable number.

18978385 is a deficient number, since it is larger than the sum of its proper divisors (3795683).

18978385 is an equidigital number, since it uses as much as digits as its factorization.

18978385 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3795682.

The product of its digits is 483840, while the sum is 49.

The square root of 18978385 is about 4356.4188274315. The cubic root of 18978385 is about 266.7389378768.

The spelling of 18978385 in words is "eighteen million, nine hundred seventy-eight thousand, three hundred eighty-five".