181817820 has 144 divisors (see below), whose sum is σ = 580900320. Its totient is φ = 45964800.

The previous prime is 181817819. The next prime is 181817837. The reversal of 181817820 is 28718181.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 318135 + ... + 318705.

It is an arithmetic number, because the mean of its divisors is an integer number (4034030).

Almost surely, 2^181817820 is an apocalyptic number.

181817820 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 181817820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (290450160).

181817820 is an abundant number, since it is smaller than the sum of its proper divisors (399082500).

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

181817820 is a wasteful number, since it uses less digits than its factorization.

181817820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 676 (or 671 counting only the distinct ones).

The product of its (nonzero) digits is 7168, while the sum is 36.

The square root of 181817820 is about 13483.9838326809. The cubic root of 181817820 is about 566.5159591533.

The spelling of 181817820 in words is "one hundred eighty-one million, eight hundred seventeen thousand, eight hundred twenty".