18138440 has 16 divisors (see below), whose sum is σ = 40811580. Its totient is φ = 7255360.

The previous prime is 18138437. The next prime is 18138443. The reversal of 18138440 is 4483181.

It is an interprime number because it is at equal distance from previous prime (18138437) and next prime (18138443).

It can be written as a sum of positive squares in 2 ways, for example, as 17656804 + 481636 = 4202^2 + 694^2 .

It is not an unprimeable number, because it can be changed into a prime (18138443) 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, 226691 + ... + 226770.

Almost surely, 2^18138440 is an apocalyptic number.

18138440 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

18138440 is an abundant number, since it is smaller than the sum of its proper divisors (22673140).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

18138440 is a wasteful number, since it uses less digits than its factorization.

18138440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 453472 (or 453468 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 29.

The square root of 18138440 is about 4258.9247469285. The cubic root of 18138440 is about 262.7443046828.

The spelling of 18138440 in words is "eighteen million, one hundred thirty-eight thousand, four hundred forty".