18356771821 has 8 divisors (see below), whose sum is σ = 18416585720. Its totient is φ = 18296990208.

The previous prime is 18356771809. The next prime is 18356771833. The reversal of 18356771821 is 12817765381.

It is an interprime number because it is at equal distance from previous prime (18356771809) and next prime (18356771833).

It can be written as a sum of positive squares in 4 ways, for example, as 7806606025 + 10550165796 = 88355^2 + 102714^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 18356771821 - 2⁵ = 18356771789 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 (18356771801) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1705585 + ... + 1716313.

It is an arithmetic number, because the mean of its divisors is an integer number (2302073215).

Almost surely, 2^18356771821 is an apocalyptic number.

It is an amenable number.

18356771821 is a deficient number, since it is larger than the sum of its proper divisors (59813899).

18356771821 is a wasteful number, since it uses less digits than its factorization.

18356771821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16143.

The product of its digits is 564480, while the sum is 49.

The spelling of 18356771821 in words is "eighteen billion, three hundred fifty-six million, seven hundred seventy-one thousand, eight hundred twenty-one".