18440820 has 72 divisors (see below), whose sum is σ = 57022056. Its totient is φ = 4822272.

The previous prime is 18440813. The next prime is 18440831. The reversal of 18440820 is 2804481.

It can be written as a sum of positive squares in 4 ways, for example, as 4691556 + 13749264 = 2166^2 + 3708^2 .

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 23 ways as a sum of consecutive naturals, for example, 8574 + ... + 10506.

It is an arithmetic number, because the mean of its divisors is an integer number (791973).

Almost surely, 2^18440820 is an apocalyptic number.

18440820 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 18440820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28511028).

18440820 is an abundant number, since it is smaller than the sum of its proper divisors (38581236).

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

18440820 is a wasteful number, since it uses less digits than its factorization.

18440820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2001 (or 1996 counting only the distinct ones).

The product of its (nonzero) digits is 2048, while the sum is 27.

The square root of 18440820 is about 4294.2775876741. The cubic root of 18440820 is about 264.1963071603.

The spelling of 18440820 in words is "eighteen million, four hundred forty thousand, eight hundred twenty".