18131821 has 8 divisors (see below), whose sum is σ = 18547200. Its totient is φ = 17720160.

The previous prime is 18131819. The next prime is 18131831. The reversal of 18131821 is 12813181.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 18131821 - 2¹ = 18131819 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 (18131831) 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 7 ways as a sum of consecutive naturals, for example, 10465 + ... + 12073.

It is an arithmetic number, because the mean of its divisors is an integer number (2318400).

Almost surely, 2^18131821 is an apocalyptic number.

It is an amenable number.

18131821 is a deficient number, since it is larger than the sum of its proper divisors (415379).

18131821 is a wasteful number, since it uses less digits than its factorization.

18131821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1859.

The product of its digits is 384, while the sum is 25.

The square root of 18131821 is about 4258.1476019509. The cubic root of 18131821 is about 262.7123409613.

The spelling of 18131821 in words is "eighteen million, one hundred thirty-one thousand, eight hundred twenty-one".