18181840 has 80 divisors (see below), whose sum is σ = 46403280. Its totient is φ = 6594560.

The previous prime is 18181831. The next prime is 18181861. The reversal of 18181840 is 4818181.

It can be written as a sum of positive squares in 8 ways, for example, as 144 + 18181696 = 12^2 + 4264^2 .

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 39210 + ... + 39670.

It is an arithmetic number, because the mean of its divisors is an integer number (580041).

Almost surely, 2^18181840 is an apocalyptic number.

18181840 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 18181840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23201640).

18181840 is an abundant number, since it is smaller than the sum of its proper divisors (28221440).

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

18181840 is a wasteful number, since it uses less digits than its factorization.

18181840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 520 (or 514 counting only the distinct ones).

The product of its (nonzero) digits is 2048, while the sum is 31.

The square root of 18181840 is about 4264.0168855200. The cubic root of 18181840 is about 262.9536946143.

The spelling of 18181840 in words is "eighteen million, one hundred eighty-one thousand, eight hundred forty".