18881389 has 2 divisors, whose sum is σ = 18881390. Its totient is φ = 18881388.

The previous prime is 18881381. The next prime is 18881411. The reversal of 18881389 is 98318881.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16540489 + 2340900 = 4067^2 + 1530^2 .

It is a cyclic number.

It is not a de Polignac number, because 18881389 - 2³ = 18881381 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18881381) 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, 9440694 + 9440695.

It is an arithmetic number, because the mean of its divisors is an integer number (9440695).

Almost surely, 2^18881389 is an apocalyptic number.

It is an amenable number.

18881389 is a deficient number, since it is larger than the sum of its proper divisors (1).

18881389 is an equidigital number, since it uses as much as digits as its factorization.

18881389 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 110592, while the sum is 46.

The square root of 18881389 is about 4345.2720283085. The cubic root of 18881389 is about 266.2837391028.

The spelling of 18881389 in words is "eighteen million, eight hundred eighty-one thousand, three hundred eighty-nine".