18151821 has 24 divisors (see below), whose sum is σ = 27899040. Its totient is φ = 11340000.

The previous prime is 18151799. The next prime is 18151849. The reversal of 18151821 is 12815181.

It is not a de Polignac number, because 18151821 - 2¹⁴ = 18135437 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18151421) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 16746 + ... + 17796.

It is an arithmetic number, because the mean of its divisors is an integer number (1162460).

Almost surely, 2^18151821 is an apocalyptic number.

It is an amenable number.

18151821 is a deficient number, since it is larger than the sum of its proper divisors (9747219).

18151821 is a wasteful number, since it uses less digits than its factorization.

18151821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1177 (or 1174 counting only the distinct ones).

The product of its digits is 640, while the sum is 27.

The square root of 18151821 is about 4260.4953937306. The cubic root of 18151821 is about 262.8088989432.

The spelling of 18151821 in words is "eighteen million, one hundred fifty-one thousand, eight hundred twenty-one".