181209820 has 48 divisors (see below), whose sum is σ = 416642688. Its totient is φ = 65655360.

The previous prime is 181209797. The next prime is 181209829. The reversal of 181209820 is 28902181.

It is a happy number.

181209820 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (181209829) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 66199 + ... + 68881.

It is an arithmetic number, because the mean of its divisors is an integer number (8680056).

Almost surely, 2^181209820 is an apocalyptic number.

181209820 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 181209820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (208321344).

181209820 is an abundant number, since it is smaller than the sum of its proper divisors (235432868).

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

181209820 is a wasteful number, since it uses less digits than its factorization.

181209820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3010 (or 3008 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 31.

The square root of 181209820 is about 13461.4196873881. The cubic root of 181209820 is about 565.8837762417.

The spelling of 181209820 in words is "one hundred eighty-one million, two hundred nine thousand, eight hundred twenty".