18381994 has 4 divisors (see below), whose sum is σ = 27572994. Its totient is φ = 9190996.

The previous prime is 18381989. The next prime is 18382003. The reversal of 18381994 is 49918381.

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., 16524225 + 1857769 = 4065^2 + 1363^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 18381994.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4595497 + ... + 4595500.

Almost surely, 2^18381994 is an apocalyptic number.

18381994 is a deficient number, since it is larger than the sum of its proper divisors (9191000).

18381994 is an equidigital number, since it uses as much as digits as its factorization.

18381994 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9190999.

The product of its digits is 62208, while the sum is 43.

The square root of 18381994 is about 4287.4227689837. The cubic root of 18381994 is about 263.9150802017.

The spelling of 18381994 in words is "eighteen million, three hundred eighty-one thousand, nine hundred ninety-four".