818221220 has 48 divisors (see below), whose sum is σ = 1822465008. Its totient is φ = 307507200.

The previous prime is 818221199. The next prime is 818221241. The reversal of 818221220 is 22122818.

It is an interprime number because it is at equal distance from previous prime (818221199) and next prime (818221241).

It can be written as a sum of positive squares in 8 ways, for example, as 30184036 + 788037184 = 5494^2 + 28072^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 818221220.

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, 236624 + ... + 240056.

It is an arithmetic number, because the mean of its divisors is an integer number (37968021).

Almost surely, 2^818221220 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 818221220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (911232504).

818221220 is an abundant number, since it is smaller than the sum of its proper divisors (1004243788).

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

818221220 is a wasteful number, since it uses less digits than its factorization.

818221220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4160 (or 4158 counting only the distinct ones).

The product of its (nonzero) digits is 1024, while the sum is 26.

The square root of 818221220 is about 28604.5664186682. The cubic root of 818221220 is about 935.3128753601.

The spelling of 818221220 in words is "eight hundred eighteen million, two hundred twenty-one thousand, two hundred twenty".