18891389 has 4 divisors (see below), whose sum is σ = 20608800. Its totient is φ = 17173980.

The previous prime is 18891371. The next prime is 18891401. The reversal of 18891389 is 98319881.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18891389 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18891329) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 858689 + ... + 858710.

It is an arithmetic number, because the mean of its divisors is an integer number (5152200).

Almost surely, 2^18891389 is an apocalyptic number.

It is an amenable number.

18891389 is a deficient number, since it is larger than the sum of its proper divisors (1717411).

18891389 is a wasteful number, since it uses less digits than its factorization.

18891389 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1717410.

The product of its digits is 124416, while the sum is 47.

The square root of 18891389 is about 4346.4225519385. The cubic root of 18891389 is about 266.3307407196.

The spelling of 18891389 in words is "eighteen million, eight hundred ninety-one thousand, three hundred eighty-nine".