18090781 has 4 divisors (see below), whose sum is σ = 18102364. Its totient is φ = 18079200.

The previous prime is 18090773. The next prime is 18090797. The reversal of 18090781 is 18709081.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 164025 + 17926756 = 405^2 + 4234^2 .

It is a cyclic number.

It is not a de Polignac number, because 18090781 - 2³ = 18090773 is a prime.

It is a super-2 number, since 2×18090781² = 654552714379922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18090181) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3000 + ... + 6721.

It is an arithmetic number, because the mean of its divisors is an integer number (4525591).

Almost surely, 2^18090781 is an apocalyptic number.

It is an amenable number.

18090781 is a deficient number, since it is larger than the sum of its proper divisors (11583).

18090781 is an equidigital number, since it uses as much as digits as its factorization.

18090781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11582.

The product of its (nonzero) digits is 4032, while the sum is 34.

The square root of 18090781 is about 4253.3258751241. The cubic root of 18090781 is about 262.5139814171.

The spelling of 18090781 in words is "eighteen million, ninety thousand, seven hundred eighty-one".