18256981 has 4 divisors (see below), whose sum is σ = 18314892. Its totient is φ = 18199072.

The previous prime is 18256969. The next prime is 18256991. The reversal of 18256981 is 18965281.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 2056356 + 16200625 = 1434^2 + 4025^2 .

It is a cyclic number.

It is not a de Polignac number, because 18256981 - 2⁵ = 18256949 is a prime.

It is a super-4 number, since 4×18256981⁴ (a number of 30 digits) contains 4444 as substring. Note that it is a super-d number also for d = 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 Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18256991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 28480 + ... + 29113.

It is an arithmetic number, because the mean of its divisors is an integer number (4578723).

Almost surely, 2^18256981 is an apocalyptic number.

It is an amenable number.

18256981 is a deficient number, since it is larger than the sum of its proper divisors (57911).

18256981 is an equidigital number, since it uses as much as digits as its factorization.

18256981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57910.

The product of its digits is 34560, while the sum is 40.

The square root of 18256981 is about 4272.8188587863. The cubic root of 18256981 is about 263.3154373710.

The spelling of 18256981 in words is "eighteen million, two hundred fifty-six thousand, nine hundred eighty-one".