18391440 has 40 divisors (see below), whose sum is σ = 57014208. Its totient is φ = 4904320.

The previous prime is 18391409. The next prime is 18391441. The reversal of 18391440 is 4419381.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (40).

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 18391398 and 18391407.

It is not an unprimeable number, because it can be changed into a prime (18391441) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 38076 + ... + 38555.

Almost surely, 2^18391440 is an apocalyptic number.

18391440 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

18391440 is an abundant number, since it is smaller than the sum of its proper divisors (38622768).

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

18391440 is a wasteful number, since it uses less digits than its factorization.

18391440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 76647 (or 76641 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 30.

The square root of 18391440 is about 4288.5242216875. The cubic root of 18391440 is about 263.9602786887.

The spelling of 18391440 in words is "eighteen million, three hundred ninety-one thousand, four hundred forty".