18381520 has 20 divisors (see below), whose sum is σ = 42737220. Its totient is φ = 7352576.

The previous prime is 18381491. The next prime is 18381521. The reversal of 18381520 is 2518381.

It can be written as a sum of positive squares in 2 ways, for example, as 5363856 + 13017664 = 2316^2 + 3608^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18381521) 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 3 ways as a sum of consecutive naturals, for example, 114805 + ... + 114964.

It is an arithmetic number, because the mean of its divisors is an integer number (2136861).

Almost surely, 2^18381520 is an apocalyptic number.

18381520 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

18381520 is an abundant number, since it is smaller than the sum of its proper divisors (24355700).

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

18381520 is a wasteful number, since it uses less digits than its factorization.

18381520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 229782 (or 229776 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 28.

The square root of 18381520 is about 4287.3674906637. The cubic root of 18381520 is about 263.9128117350.

The spelling of 18381520 in words is "eighteen million, three hundred eighty-one thousand, five hundred twenty".