18106821 has 20 divisors (see below), whose sum is σ = 27924864. Its totient is φ = 11680200.

The previous prime is 18106787. The next prime is 18106831. The reversal of 18106821 is 12860181.

It is not a de Polignac number, because 18106821 - 2⁶ = 18106757 is a prime.

It is a Smith number, since the sum of its digits (27) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18106831) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 1095 + ... + 6116.

Almost surely, 2^18106821 is an apocalyptic number.

It is an amenable number.

18106821 is a deficient number, since it is larger than the sum of its proper divisors (9818043).

18106821 is an equidigital number, since it uses as much as digits as its factorization.

18106821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7254 (or 7245 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 27.

The square root of 18106821 is about 4255.2110405948. The cubic root of 18106821 is about 262.5915435818.

The spelling of 18106821 in words is "eighteen million, one hundred six thousand, eight hundred twenty-one".