18009778 has 4 divisors (see below), whose sum is σ = 27014670. Its totient is φ = 9004888.

The previous prime is 18009763. The next prime is 18009821. The reversal of 18009778 is 87790081.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 87790081 = 1901 ⋅46181.

It can be written as a sum of positive squares in only one way, i.e., 17665209 + 344569 = 4203^2 + 587^2 .

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 18009778.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4502443 + ... + 4502446.

Almost surely, 2^18009778 is an apocalyptic number.

18009778 is a deficient number, since it is larger than the sum of its proper divisors (9004892).

18009778 is an equidigital number, since it uses as much as digits as its factorization.

18009778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9004891.

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

The square root of 18009778 is about 4243.7928790175. The cubic root of 18009778 is about 262.1215856628.

The spelling of 18009778 in words is "eighteen million, nine thousand, seven hundred seventy-eight".