1821220 has 24 divisors (see below), whose sum is σ = 3919608. Its totient is φ = 710400.

The previous prime is 1821191. The next prime is 1821233. The reversal of 1821220 is 221281.

It can be written as a sum of positive squares in 4 ways, for example, as 30976 + 1790244 = 176^2 + 1338^2 .

It is a junction number, because it is equal to n+sod(n) for n = 1821194 and 1821203.

It is a congruent number.

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, 291 + ... + 1930.

It is an arithmetic number, because the mean of its divisors is an integer number (163317).

2^1821220 is an apocalyptic number.

1821220 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1821220 is an abundant number, since it is smaller than the sum of its proper divisors (2098388).

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

1821220 is a wasteful number, since it uses less digits than its factorization.

1821220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2271 (or 2269 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 16.

The square root of 1821220 is about 1349.5258426573. The cubic root of 1821220 is about 122.1201897157.

The spelling of 1821220 in words is "one million, eight hundred twenty-one thousand, two hundred twenty".