18121111 has 4 divisors (see below), whose sum is σ = 18143800. Its totient is φ = 18098424.

The previous prime is 18121093. The next prime is 18121123. The reversal of 18121111 is 11112181.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 11112181 = 523 ⋅21247.

It is a cyclic number.

It is not a de Polignac number, because 18121111 - 2¹¹ = 18119063 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 (18121151) 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, 10101 + ... + 11758.

It is an arithmetic number, because the mean of its divisors is an integer number (4535950).

Almost surely, 2^18121111 is an apocalyptic number.

18121111 is a deficient number, since it is larger than the sum of its proper divisors (22689).

18121111 is an equidigital number, since it uses as much as digits as its factorization.

18121111 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22688.

The product of its digits is 16, while the sum is 16.

The square root of 18121111 is about 4256.8898270921. The cubic root of 18121111 is about 262.6606049675.

Adding to 18121111 its reverse (11112181), we get a palindrome (29233292).

The spelling of 18121111 in words is "eighteen million, one hundred twenty-one thousand, one hundred eleven".