816221220 has 24 divisors (see below), whose sum is σ = 2285419584. Its totient is φ = 217658976.

The previous prime is 816221213. The next prime is 816221239. The reversal of 816221220 is 22122618.

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 7 ways as a sum of consecutive naturals, for example, 6801784 + ... + 6801903.

It is an arithmetic number, because the mean of its divisors is an integer number (95225816).

Almost surely, 2^816221220 is an apocalyptic number.

It is an amenable number.

816221220 is an abundant number, since it is smaller than the sum of its proper divisors (1469198364).

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

816221220 is a wasteful number, since it uses less digits than its factorization.

816221220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13603699 (or 13603697 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 24.

The square root of 816221220 is about 28569.5855762732. The cubic root of 816221220 is about 934.5501835118.

Adding to 816221220 its reverse (22122618), we get a palindrome (838343838).

The spelling of 816221220 in words is "eight hundred sixteen million, two hundred twenty-one thousand, two hundred twenty".