18973821 has 16 divisors (see below), whose sum is σ = 25790400. Its totient is φ = 12405888.

The previous prime is 18973807. The next prime is 18973831. The reversal of 18973821 is 12837981.

It is not a de Polignac number, because 18973821 - 2¹⁰ = 18972797 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 18973821.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18973831) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 47595 + ... + 47991.

It is an arithmetic number, because the mean of its divisors is an integer number (1611900).

Almost surely, 2^18973821 is an apocalyptic number.

It is an amenable number.

18973821 is a deficient number, since it is larger than the sum of its proper divisors (6816579).

18973821 is a wasteful number, since it uses less digits than its factorization.

18973821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 668.

The product of its digits is 24192, while the sum is 39.

The square root of 18973821 is about 4355.8949711856. The cubic root of 18973821 is about 266.7175540040.

The spelling of 18973821 in words is "eighteen million, nine hundred seventy-three thousand, eight hundred twenty-one".