18021840 has 80 divisors (see below), whose sum is σ = 56829696. Its totient is φ = 4723200.

The previous prime is 18021827. The next prime is 18021841. The reversal of 18021840 is 4812081.

It is a tau number, because it is divible by the number of its divisors (80).

It is a hoax number, since the sum of its digits (24) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 18021840.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18021841) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 14025 + ... + 15255.

Almost surely, 2^18021840 is an apocalyptic number.

18021840 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 18021840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28414848).

18021840 is an abundant number, since it is smaller than the sum of its proper divisors (38807856).

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

18021840 is a wasteful number, since it uses less digits than its factorization.

18021840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1308 (or 1302 counting only the distinct ones).

The product of its (nonzero) digits is 512, while the sum is 24.

The square root of 18021840 is about 4245.2137755359. The cubic root of 18021840 is about 262.1800910106.

The spelling of 18021840 in words is "eighteen million, twenty-one thousand, eight hundred forty".