18201821921 has 8 divisors (see below), whose sum is σ = 18696002280. Its totient is φ = 17707759488.

The previous prime is 18201821893. The next prime is 18201821923. The reversal of 18201821921 is 12912810281.

It can be written as a sum of positive squares in 4 ways, for example, as 10560439696 + 7641382225 = 102764^2 + 87415^2 .

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 18201821921 - 2¹⁸ = 18201559777 is a prime.

It is a super-2 number, since 2×18201821921² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18201821923) 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, 348125 + ... + 396981.

It is an arithmetic number, because the mean of its divisors is an integer number (2337000285).

Almost surely, 2^18201821921 is an apocalyptic number.

It is an amenable number.

18201821921 is a deficient number, since it is larger than the sum of its proper divisors (494180359).

18201821921 is a wasteful number, since it uses less digits than its factorization.

18201821921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 58963.

The product of its (nonzero) digits is 4608, while the sum is 35.

The spelling of 18201821921 in words is "eighteen billion, two hundred one million, eight hundred twenty-one thousand, nine hundred twenty-one".