18689821 has 4 divisors (see below), whose sum is σ = 19124512. Its totient is φ = 18255132.

The previous prime is 18689819. The next prime is 18689837. The reversal of 18689821 is 12898681.

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.

It is a cyclic number.

It is not a de Polignac number, because 18689821 - 2¹ = 18689819 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (43), and also a Moran number because the ratio is a prime number: 434647 = 18689821 / (1 + 8 + 6 + 8 + 9 + 8 + 2 + 1).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18684821) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 217281 + ... + 217366.

It is an arithmetic number, because the mean of its divisors is an integer number (4781128).

Almost surely, 2^18689821 is an apocalyptic number.

It is an amenable number.

18689821 is a deficient number, since it is larger than the sum of its proper divisors (434691).

18689821 is an equidigital number, since it uses as much as digits as its factorization.

18689821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 434690.

The product of its digits is 55296, while the sum is 43.

The square root of 18689821 is about 4323.1725619040. The cubic root of 18689821 is about 265.3801166564.

The spelling of 18689821 in words is "eighteen million, six hundred eighty-nine thousand, eight hundred twenty-one".