18388881 has 12 divisors (see below), whose sum is σ = 30356352. Its totient is φ = 10507896.

The previous prime is 18388879. The next prime is 18388957. The reversal of 18388881 is 18888381.

It is a happy number.

It is not a de Polignac number, because 18388881 - 2¹ = 18388879 is a prime.

It is a super-2 number, since 2×18388881² = 676301888864322, which contains 22 as substring.

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (18388831) 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 in 11 ways as a sum of consecutive naturals, for example, 145881 + ... + 146006.

It is an arithmetic number, because the mean of its divisors is an integer number (2529696).

Almost surely, 2^18388881 is an apocalyptic number.

It is an amenable number.

18388881 is a deficient number, since it is larger than the sum of its proper divisors (11967471).

18388881 is a wasteful number, since it uses less digits than its factorization.

18388881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 291900 (or 291897 counting only the distinct ones).

The product of its digits is 98304, while the sum is 45.

The square root of 18388881 is about 4288.2258569250. The cubic root of 18388881 is about 263.9480355712.

Subtracting 18388881 from its reverse (18888381), we obtain a triangular number (499500 = T₉₉₉).

The spelling of 18388881 in words is "eighteen million, three hundred eighty-eight thousand, eight hundred eighty-one".