18721111 has 4 divisors (see below), whose sum is σ = 18737712. Its totient is φ = 18704512.

The previous prime is 18721091. The next prime is 18721123. The reversal of 18721111 is 11112781.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 11112781 = 17 ⋅653693.

It is a cyclic number.

It is not a de Polignac number, because 18721111 - 2⁹ = 18720599 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 (18721141) 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, 6475 + ... + 8908.

It is an arithmetic number, because the mean of its divisors is an integer number (4684428).

Almost surely, 2^18721111 is an apocalyptic number.

18721111 is a deficient number, since it is larger than the sum of its proper divisors (16601).

18721111 is a wasteful number, since it uses less digits than its factorization.

18721111 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16600.

The product of its digits is 112, while the sum is 22.

The square root of 18721111 is about 4326.7899186348. The cubic root of 18721111 is about 265.5281315248.

Adding to 18721111 its reverse (11112781), we get a palindrome (29833892).

The spelling of 18721111 in words is "eighteen million, seven hundred twenty-one thousand, one hundred eleven".