18387840 has 128 divisors (see below), whose sum is σ = 59951520. Its totient is φ = 4792320.

The previous prime is 18387821. The next prime is 18387841. The reversal of 18387840 is 4878381.

18387840 is nontrivially palindromic in base 13.

It is a tau number, because it is divible by the number of its divisors (128).

It is a super-2 number, since 2×18387840² = 676225319731200, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18387841) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 117042 + ... + 117198.

Almost surely, 2^18387840 is an apocalyptic number.

18387840 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 18387840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29975760).

18387840 is an abundant number, since it is smaller than the sum of its proper divisors (41563680).

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

18387840 is a wasteful number, since it uses less digits than its factorization.

18387840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 240 (or 228 counting only the distinct ones).

The product of its (nonzero) digits is 43008, while the sum is 39.

The square root of 18387840 is about 4288.1044763392. The cubic root of 18387840 is about 263.9430547517.

The spelling of 18387840 in words is "eighteen million, three hundred eighty-seven thousand, eight hundred forty".