18387891 has 10 divisors (see below), whose sum is σ = 27468452. Its totient is φ = 12258540.

The previous prime is 18387883. The next prime is 18387917. The reversal of 18387891 is 19878381.

It is not a de Polignac number, because 18387891 - 2³ = 18387883 is a prime.

It is a super-2 number, since 2×18387891² = 676229070855762, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18387821) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 113425 + ... + 113586.

Almost surely, 2^18387891 is an apocalyptic number.

18387891 is a deficient number, since it is larger than the sum of its proper divisors (9080561).

18387891 is an equidigital number, since it uses as much as digits as its factorization.

18387891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 227023 (or 227014 counting only the distinct ones).

The product of its digits is 96768, while the sum is 45.

The square root of 18387891 is about 4288.1104230185. The cubic root of 18387891 is about 263.9432987731.

The spelling of 18387891 in words is "eighteen million, three hundred eighty-seven thousand, eight hundred ninety-one".