18012781 has 4 divisors (see below), whose sum is σ = 18021532. Its totient is φ = 18004032.

The previous prime is 18012763. The next prime is 18012793. The reversal of 18012781 is 18721081.

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, and also an emirpimes, since its reverse is a distinct semiprime: 18721081 = 677 ⋅27653.

It can be written as a sum of positive squares in 2 ways, for example, as 13875625 + 4137156 = 3725^2 + 2034^2 .

It is a cyclic number.

It is not a de Polignac number, because 18012781 - 2¹⁷ = 17881709 is a prime.

It is a super-2 number, since 2×18012781² = 648920558707922, 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 (18012721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 595 + ... + 6031.

It is an arithmetic number, because the mean of its divisors is an integer number (4505383).

Almost surely, 2^18012781 is an apocalyptic number.

It is an amenable number.

18012781 is a deficient number, since it is larger than the sum of its proper divisors (8751).

18012781 is an equidigital number, since it uses as much as digits as its factorization.

18012781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8750.

The product of its (nonzero) digits is 896, while the sum is 28.

The square root of 18012781 is about 4244.1466751280. The cubic root of 18012781 is about 262.1361538115.

The spelling of 18012781 in words is "eighteen million, twelve thousand, seven hundred eighty-one".