821220 has 24 divisors (see below), whose sum is σ = 2299584. Its totient is φ = 218976.

The previous prime is 821209. The next prime is 821263. The reversal of 821220 is 22128.

821220 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 821220.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6784 + ... + 6903.

It is an arithmetic number, because the mean of its divisors is an integer number (95816).

2⁸²¹²²⁰ is an apocalyptic number.

It is an amenable number.

821220 is an abundant number, since it is smaller than the sum of its proper divisors (1478364).

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

821220 is a wasteful number, since it uses less digits than its factorization.

821220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13699 (or 13697 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 15.

The square root of 821220 is about 906.2118957507. The cubic root of 821220 is about 93.6454122539.

Adding to 821220 its reverse (22128), we get a palindrome (843348).

The spelling of 821220 in words is "eight hundred twenty-one thousand, two hundred twenty".