18961321 has 2 divisors, whose sum is σ = 18961322. Its totient is φ = 18961320.

The previous prime is 18961289. The next prime is 18961339. The reversal of 18961321 is 12316981.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15681600 + 3279721 = 3960^2 + 1811^2 .

It is a cyclic number.

It is not a de Polignac number, because 18961321 - 2⁵ = 18961289 is a prime.

It is not a weakly prime, because it can be changed into another prime (18961381) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9480660 + 9480661.

It is an arithmetic number, because the mean of its divisors is an integer number (9480661).

Almost surely, 2^18961321 is an apocalyptic number.

It is an amenable number.

18961321 is a deficient number, since it is larger than the sum of its proper divisors (1).

18961321 is an equidigital number, since it uses as much as digits as its factorization.

18961321 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2592, while the sum is 31.

The square root of 18961321 is about 4354.4598976222. The cubic root of 18961321 is about 266.6589697431.

The spelling of 18961321 in words is "eighteen million, nine hundred sixty-one thousand, three hundred twenty-one".