18994978 has 4 divisors (see below), whose sum is σ = 28492470. Its totient is φ = 9497488.

The previous prime is 18994907. The next prime is 18994979. The reversal of 18994978 is 87949981.

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

It can be written as a sum of positive squares in only one way, i.e., 14845609 + 4149369 = 3853^2 + 2037^2 .

It is not an unprimeable number, because it can be changed into a prime (18994979) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4748743 + ... + 4748746.

Almost surely, 2^18994978 is an apocalyptic number.

18994978 is a deficient number, since it is larger than the sum of its proper divisors (9497492).

18994978 is an equidigital number, since it uses as much as digits as its factorization.

18994978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9497491.

The product of its digits is 1306368, while the sum is 55.

The square root of 18994978 is about 4358.3228425623. The cubic root of 18994978 is about 266.8166527776.

The spelling of 18994978 in words is "eighteen million, nine hundred ninety-four thousand, nine hundred seventy-eight".