18321918328921 has 9 divisors (see below), whose sum is σ = 18339652093791. Its totient is φ = 18304201707792.

The previous prime is 18321918328907. The next prime is 18321918328927. The reversal of 18321918328921 is 12982381912381.

The square root of 18321918328921 is 4280411.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 830586163225 + 17491332165696 = 911365^2 + 4182264^2 .

It is a de Polignac number, because none of the positive numbers 2^k-18321918328921 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18321918328927) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 8573662165 + ... + 8573664301.

Almost surely, 2^{18321918328921} is an apocalyptic number.

18321918328921 is the 4280411-st square number.

18321918328921 is the 2140206-th centered octagonal number.

It is an amenable number.

18321918328921 is a deficient number, since it is larger than the sum of its proper divisors (17733764870).

18321918328921 is an frugal number, since it uses more digits than its factorization.

18321918328921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8280 (or 4140 counting only the distinct ones).

The product of its digits is 2985984, while the sum is 58.

The spelling of 18321918328921 in words is "eighteen trillion, three hundred twenty-one billion, nine hundred eighteen million, three hundred twenty-eight thousand, nine hundred twenty-one".