18642821 has 4 divisors (see below), whose sum is σ = 18652512. Its totient is φ = 18633132.

The previous prime is 18642809. The next prime is 18642839. The reversal of 18642821 is 12824681.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 18642821 - 2¹⁴ = 18626437 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18642851) 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, 875 + ... + 6168.

It is an arithmetic number, because the mean of its divisors is an integer number (4663128).

Almost surely, 2^18642821 is an apocalyptic number.

It is an amenable number.

18642821 is a deficient number, since it is larger than the sum of its proper divisors (9691).

18642821 is an equidigital number, since it uses as much as digits as its factorization.

18642821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9690.

The product of its digits is 6144, while the sum is 32.

The square root of 18642821 is about 4317.7333173785. The cubic root of 18642821 is about 265.1574761177.

The spelling of 18642821 in words is "eighteen million, six hundred forty-two thousand, eight hundred twenty-one".