18919381 has 6 divisors (see below), whose sum is σ = 20486850. Its totient is φ = 17463888.

The previous prime is 18919379. The next prime is 18919391. The reversal of 18919381 is 18391981.

It is a happy number.

It can be written as a sum of positive squares in 3 ways, for example, as 2387025 + 16532356 = 1545^2 + 4066^2 .

It is not a de Polignac number, because 18919381 - 2¹ = 18919379 is a prime.

It is a super-2 number, since 2×18919381² = 715885954846322, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18919361) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 55806 + ... + 56143.

It is an arithmetic number, because the mean of its divisors is an integer number (3414475).

Almost surely, 2^18919381 is an apocalyptic number.

It is an amenable number.

18919381 is a deficient number, since it is larger than the sum of its proper divisors (1567469).

18919381 is a wasteful number, since it uses less digits than its factorization.

18919381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 111975 (or 111962 counting only the distinct ones).

The product of its digits is 15552, while the sum is 40.

The square root of 18919381 is about 4349.6414794785. The cubic root of 18919381 is about 266.4622195104.

The spelling of 18919381 in words is "eighteen million, nine hundred nineteen thousand, three hundred eighty-one".