20818111 has 4 divisors (see below), whose sum is σ = 20830824. Its totient is φ = 20805400.

The previous prime is 20818099. The next prime is 20818121. The reversal of 20818111 is 11181802.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 20818111 - 2⁷ = 20817983 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 (20818121) 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, 3460 + ... + 7321.

It is an arithmetic number, because the mean of its divisors is an integer number (5207706).

Almost surely, 2^20818111 is an apocalyptic number.

20818111 is a deficient number, since it is larger than the sum of its proper divisors (12713).

20818111 is a wasteful number, since it uses less digits than its factorization.

20818111 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12712.

The product of its (nonzero) digits is 128, while the sum is 22.

The square root of 20818111 is about 4562.6868180930. The cubic root of 20818111 is about 275.0935703624.

Adding to 20818111 its reverse (11181802), we get a palindrome (31999913).

The spelling of 20818111 in words is "twenty million, eight hundred eighteen thousand, one hundred eleven".