181213220 has 12 divisors (see below), whose sum is σ = 380547804. Its totient is φ = 72485280.

The previous prime is 181213189. The next prime is 181213237. The reversal of 181213220 is 22312181.

It can be written as a sum of positive squares in 2 ways, for example, as 31787044 + 149426176 = 5638^2 + 12224^2 .

It is a super-2 number, since 2×181213220² = 65676462205536800, which contains 22 as substring.

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: 9060661 = 181213220 / (1 + 8 + 1 + 2 + 1 + 3 + 2 + 2 + 0).

It is a junction number, because it is equal to n+sod(n) for n = 181213192 and 181213201.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4530311 + ... + 4530350.

It is an arithmetic number, because the mean of its divisors is an integer number (31712317).

Almost surely, 2^181213220 is an apocalyptic number.

181213220 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

181213220 is an abundant number, since it is smaller than the sum of its proper divisors (199334584).

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

181213220 is a wasteful number, since it uses less digits than its factorization.

181213220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9060670 (or 9060668 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 20.

The square root of 181213220 is about 13461.5459736243. The cubic root of 181213220 is about 565.8873154038.

The spelling of 181213220 in words is "one hundred eighty-one million, two hundred thirteen thousand, two hundred twenty".