18161861 has 4 divisors (see below), whose sum is σ = 18170400. Its totient is φ = 18153324.

The previous prime is 18161851. The next prime is 18161903. The reversal of 18161861 is 16816181.

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 a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 16816181 = 983 ⋅17107.

It is a cyclic number.

It is not a de Polignac number, because 18161861 - 2¹⁰ = 18160837 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18161851) 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, 1760 + ... + 6278.

It is an arithmetic number, because the mean of its divisors is an integer number (4542600).

Almost surely, 2^18161861 is an apocalyptic number.

It is an amenable number.

18161861 is a deficient number, since it is larger than the sum of its proper divisors (8539).

18161861 is an equidigital number, since it uses as much as digits as its factorization.

18161861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8538.

The product of its digits is 2304, while the sum is 32.

The square root of 18161861 is about 4261.6734975828. The cubic root of 18161861 is about 262.8573443125.

The spelling of 18161861 in words is "eighteen million, one hundred sixty-one thousand, eight hundred sixty-one".