181220 has 48 divisors (see below), whose sum is σ = 444528. Its totient is φ = 61440.

The previous prime is 181219. The next prime is 181243. The reversal of 181220 is 22181.

Added to its reverse (22181) it gives a square (203401 = 451²).

181220 is digitally balanced in base 2 and base 3, because in such bases it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 8 ways, for example, as 27556 + 153664 = 166^2 + 392^2 .

It is a junction number, because it is equal to n+sod(n) for n = 181195 and 181204.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 181220.

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, 4400 + ... + 4440.

It is an arithmetic number, because the mean of its divisors is an integer number (9261).

2¹⁸¹²²⁰ is an apocalyptic number.

181220 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 181220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (222264).

181220 is an abundant number, since it is smaller than the sum of its proper divisors (263308).

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

181220 is a wasteful number, since it uses less digits than its factorization.

181220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80 (or 78 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 14.

The square root of 181220 is about 425.6994244769. The cubic root of 181220 is about 56.5894372777.

Adding to 181220 its reverse (22181), we get a square (203401 = 451²).

The spelling of 181220 in words is "one hundred eighty-one thousand, two hundred twenty".