181820 has 12 divisors (see below), whose sum is σ = 381864. Its totient is φ = 72720.

The previous prime is 181813. The next prime is 181837. The reversal of 181820 is 28181.

181820 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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: 9091 = 181820 / (1 + 8 + 1 + 8 + 2 + 0).

It is a junction number, because it is equal to n+sod(n) for n = 181792 and 181801.

It is a congruent number.

It is an unprimeable number.

181820 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4526 + ... + 4565.

It is an arithmetic number, because the mean of its divisors is an integer number (31822).

2¹⁸¹⁸²⁰ is an apocalyptic number.

181820 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

181820 is an abundant number, since it is smaller than the sum of its proper divisors (200044).

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

181820 is a wasteful number, since it uses less digits than its factorization.

181820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9100 (or 9098 counting only the distinct ones).

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

The square root of 181820 is about 426.4035647131. The cubic root of 181820 is about 56.6518223324.

It can be divided in two parts, 181 and 820, that added together give a palindrome (1001).

The spelling of 181820 in words is "one hundred eighty-one thousand, eight hundred twenty".