18699821 has 6 divisors (see below), whose sum is σ = 21752910. Its totient is φ = 16028376.

The previous prime is 18699803. The next prime is 18699823. The reversal of 18699821 is 12899681.

It can be written as a sum of positive squares in only one way, i.e., 17522596 + 1177225 = 4186^2 + 1085^2 .

It is a de Polignac number, because none of the positive numbers 2^k-18699821 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 (18699823) 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 5 ways as a sum of consecutive naturals, for example, 190766 + ... + 190863.

It is an arithmetic number, because the mean of its divisors is an integer number (3625485).

Almost surely, 2^18699821 is an apocalyptic number.

It is an amenable number.

18699821 is a deficient number, since it is larger than the sum of its proper divisors (3053089).

18699821 is an equidigital number, since it uses as much as digits as its factorization.

18699821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 381643 (or 381636 counting only the distinct ones).

The product of its digits is 62208, while the sum is 44.

The square root of 18699821 is about 4324.3289652847. The cubic root of 18699821 is about 265.4274388146.

The spelling of 18699821 in words is "eighteen million, six hundred ninety-nine thousand, eight hundred twenty-one".