18259681 has 4 divisors (see below), whose sum is σ = 19919664. Its totient is φ = 16599700.

The previous prime is 18259673. The next prime is 18259687. The reversal of 18259681 is 18695281.

It is the 1745-th star number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 18695281 = 11 ⋅1699571.

It is a cyclic number.

It is not a de Polignac number, because 18259681 - 2³ = 18259673 is a prime.

It is a super-2 number, since 2×18259681² = 666831900443522, which contains 22 as substring.

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 not an unprimeable number, because it can be changed into a prime (18259687) 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, 829975 + ... + 829996.

It is an arithmetic number, because the mean of its divisors is an integer number (4979916).

Almost surely, 2^18259681 is an apocalyptic number.

18259681 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

18259681 is a deficient number, since it is larger than the sum of its proper divisors (1659983).

18259681 is a wasteful number, since it uses less digits than its factorization.

18259681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1659982.

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

The square root of 18259681 is about 4273.1347977802. The cubic root of 18259681 is about 263.3284171847.

Subtracting 18259681 from its reverse (18695281), we obtain a square (435600 = 660²).

The spelling of 18259681 in words is "eighteen million, two hundred fifty-nine thousand, six hundred eighty-one".