18520321 has 2 divisors, whose sum is σ = 18520322. Its totient is φ = 18520320.

The previous prime is 18520291. The next prime is 18520339. The reversal of 18520321 is 12302581.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11289600 + 7230721 = 3360^2 + 2689^2 .

It is an emirp because it is prime and its reverse (12302581) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18520321 is a prime.

It is a Chen prime.

It is equal to p_1182361 and since 18520321 and 1182361 have the same sum of digits, it is a Honaker prime.

It is a junction number, because it is equal to n+sod(n) for n = 18520292 and 18520301.

It is not a weakly prime, because it can be changed into another prime (18520391) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9260160 + 9260161.

It is an arithmetic number, because the mean of its divisors is an integer number (9260161).

Almost surely, 2^18520321 is an apocalyptic number.

It is an amenable number.

18520321 is a deficient number, since it is larger than the sum of its proper divisors (1).

18520321 is an equidigital number, since it uses as much as digits as its factorization.

18520321 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 480, while the sum is 22.

The square root of 18520321 is about 4303.5242534462. The cubic root of 18520321 is about 264.5754254992.

The spelling of 18520321 in words is "eighteen million, five hundred twenty thousand, three hundred twenty-one".