18090778 has 4 divisors (see below), whose sum is σ = 27136170. Its totient is φ = 9045388.

The previous prime is 18090773. The next prime is 18090797. The reversal of 18090778 is 87709081.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 87709081 = 997 ⋅87973.

It can be written as a sum of positive squares in only one way, i.e., 17833729 + 257049 = 4223^2 + 507^2 .

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a self number, because there is not a number n which added to its sum of digits gives 18090778.

It is not an unprimeable number, because it can be changed into a prime (18090773) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4522693 + ... + 4522696.

Almost surely, 2^18090778 is an apocalyptic number.

18090778 is a deficient number, since it is larger than the sum of its proper divisors (9045392).

18090778 is an equidigital number, since it uses as much as digits as its factorization.

18090778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9045391.

The product of its (nonzero) digits is 28224, while the sum is 40.

The square root of 18090778 is about 4253.3255224589. The cubic root of 18090778 is about 262.5139669061.

The spelling of 18090778 in words is "eighteen million, ninety thousand, seven hundred seventy-eight".