18309840 has 160 divisors (see below), whose sum is σ = 61710336. Its totient is φ = 4477440.

The previous prime is 18309829. The next prime is 18309847. The reversal of 18309840 is 4890381.

It is a Cunningham number, because it is equal to 4279²-1.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18309847) by changing a digit.

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 31 ways as a sum of consecutive naturals, for example, 171067 + ... + 171173.

Almost surely, 2^18309840 is an apocalyptic number.

18309840 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 18309840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30855168).

18309840 is an abundant number, since it is smaller than the sum of its proper divisors (43400496).

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

18309840 is a wasteful number, since it uses less digits than its factorization.

18309840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 177 (or 171 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 33.

The square root of 18309840 is about 4278.9998831503. Note that the first 3 decimals coincide. The cubic root of 18309840 is about 263.5693161393.

The spelling of 18309840 in words is "eighteen million, three hundred nine thousand, eight hundred forty".