18031861 has 4 divisors (see below), whose sum is σ = 18106924. Its totient is φ = 17956800.

The previous prime is 18031843. The next prime is 18031873. The reversal of 18031861 is 16813081.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 16813081 = 19 ⋅884899.

It can be written as a sum of positive squares in 2 ways, for example, as 10929636 + 7102225 = 3306^2 + 2665^2 .

It is a cyclic number.

It is not a de Polignac number, because 18031861 - 2⁷ = 18031733 is a prime.

It is a super-2 number, since 2×18031861² = 650296022246642, 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 (18031561) 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, 37170 + ... + 37651.

It is an arithmetic number, because the mean of its divisors is an integer number (4526731).

Almost surely, 2^18031861 is an apocalyptic number.

It is an amenable number.

18031861 is a deficient number, since it is larger than the sum of its proper divisors (75063).

18031861 is an equidigital number, since it uses as much as digits as its factorization.

18031861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 75062.

The product of its (nonzero) digits is 1152, while the sum is 28.

The square root of 18031861 is about 4246.3938818720. The cubic root of 18031861 is about 262.2286768722.

It can be divided in two parts, 180 and 31861, that added together give a square (32041 = 179²).

The spelling of 18031861 in words is "eighteen million, thirty-one thousand, eight hundred sixty-one".