18001800 has 144 divisors (see below), whose sum is σ = 61731540. Its totient is φ = 4700160.

The previous prime is 18001729. The next prime is 18001811. The reversal of 18001800 is 810081.

It is a happy number.

It can be written as a sum of positive squares in 6 ways, for example, as 7851204 + 10150596 = 2802^2 + 3186^2 .

It is a Harshad number since it is a multiple of its sum of digits (18).

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 35 ways as a sum of consecutive naturals, for example, 131332 + ... + 131468.

Almost surely, 2^18001800 is an apocalyptic number.

18001800 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 18001800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30865770).

18001800 is an abundant number, since it is smaller than the sum of its proper divisors (43729740).

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

18001800 is a wasteful number, since it uses less digits than its factorization.

18001800 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 232 (or 220 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 18.

The square root of 18001800 is about 4242.8528138506. The cubic root of 18001800 is about 262.0828749344.

Adding to 18001800 its reverse (810081), we get a palindrome (18811881).

It can be divided in two parts, 1800 and 1800, that added together give a square (3600 = 60²).

The spelling of 18001800 in words is "eighteen million, one thousand, eight hundred".