18919821 has 8 divisors (see below), whose sum is σ = 25640224. Its totient is φ = 12406320.

The previous prime is 18919811. The next prime is 18919841. The reversal of 18919821 is 12891981.

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

It is not a de Polignac number, because 18919821 - 2⁶ = 18919757 is a prime.

It is a Duffinian number.

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 18919821.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18919811) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 51511 + ... + 51876.

It is an arithmetic number, because the mean of its divisors is an integer number (3205028).

Almost surely, 2^18919821 is an apocalyptic number.

It is an amenable number.

18919821 is a deficient number, since it is larger than the sum of its proper divisors (6720403).

18919821 is a wasteful number, since it uses less digits than its factorization.

18919821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 103451.

The product of its digits is 10368, while the sum is 39.

The square root of 18919821 is about 4349.6920580657. The cubic root of 18919821 is about 266.4642851606.

The spelling of 18919821 in words is "eighteen million, nine hundred nineteen thousand, eight hundred twenty-one".