18128891 has 4 divisors (see below), whose sum is σ = 19776984. Its totient is φ = 16480800.

The previous prime is 18128879. The next prime is 18128897. The reversal of 18128891 is 19882181.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 18128891 - 2⁶ = 18128827 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18128897) 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, 824030 + ... + 824051.

It is an arithmetic number, because the mean of its divisors is an integer number (4944246).

Almost surely, 2^18128891 is an apocalyptic number.

18128891 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

18128891 is a deficient number, since it is larger than the sum of its proper divisors (1648093).

18128891 is a wasteful number, since it uses less digits than its factorization.

18128891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1648092.

The product of its digits is 9216, while the sum is 38.

The square root of 18128891 is about 4257.8035417337. The cubic root of 18128891 is about 262.6981892548.

The spelling of 18128891 in words is "eighteen million, one hundred twenty-eight thousand, eight hundred ninety-one".