18001820 has 12 divisors (see below), whose sum is σ = 37803864. Its totient is φ = 7200720.

The previous prime is 18001817. The next prime is 18001843. The reversal of 18001820 is 2810081.

It is a Harshad number since it is a multiple of its sum of digits (20), and also a Moran number because the ratio is a prime number: 900091 = 18001820 / (1 + 8 + 0 + 0 + 1 + 8 + 2 + 0).

It is a junction number, because it is equal to n+sod(n) for n = 18001792 and 18001801.

It is a congruent number.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 450026 + ... + 450065.

It is an arithmetic number, because the mean of its divisors is an integer number (3150322).

Almost surely, 2^18001820 is an apocalyptic number.

18001820 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

18001820 is an abundant number, since it is smaller than the sum of its proper divisors (19802044).

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

18001820 is a wasteful number, since it uses less digits than its factorization.

18001820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 900100 (or 900098 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 20.

The square root of 18001820 is about 4242.8551707547. The cubic root of 18001820 is about 262.0829719923.

The spelling of 18001820 in words is "eighteen million, one thousand, eight hundred twenty".