18191840 has 48 divisors (see below), whose sum is σ = 43645392. Its totient is φ = 7163904.

The previous prime is 18191837. The next prime is 18191869. The reversal of 18191840 is 4819181.

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a junction number, because it is equal to n+sod(n) for n = 18191797 and 18191806.

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 9872 + ... + 11568.

It is an arithmetic number, because the mean of its divisors is an integer number (909279).

Almost surely, 2^18191840 is an apocalyptic number.

18191840 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 18191840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21822696).

18191840 is an abundant number, since it is smaller than the sum of its proper divisors (25453552).

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

18191840 is a wasteful number, since it uses less digits than its factorization.

18191840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1779 (or 1771 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 32.

The square root of 18191840 is about 4265.1893275680. The cubic root of 18191840 is about 263.0018938984.

The spelling of 18191840 in words is "eighteen million, one hundred ninety-one thousand, eight hundred forty".