18504821 has 4 divisors (see below), whose sum is σ = 18674700. Its totient is φ = 18334944.

The previous prime is 18504713. The next prime is 18504833. The reversal of 18504821 is 12840581.

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

It can be written as a sum of positive squares in 2 ways, for example, as 16851025 + 1653796 = 4105^2 + 1286^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18504821 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 (18504851) 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 3 ways as a sum of consecutive naturals, for example, 84776 + ... + 84993.

It is an arithmetic number, because the mean of its divisors is an integer number (4668675).

Almost surely, 2^18504821 is an apocalyptic number.

It is an amenable number.

18504821 is a deficient number, since it is larger than the sum of its proper divisors (169879).

18504821 is a wasteful number, since it uses less digits than its factorization.

18504821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 169878.

The product of its (nonzero) digits is 2560, while the sum is 29.

The square root of 18504821 is about 4301.7230268812. The cubic root of 18504821 is about 264.5015955393.

The spelling of 18504821 in words is "eighteen million, five hundred four thousand, eight hundred twenty-one".