1811821820 has 24 divisors (see below), whose sum is σ = 3830029728. Its totient is φ = 719928000.

The previous prime is 1811821769. The next prime is 1811821901. The reversal of 1811821820 is 281281181.

It is a super-2 number, since 2×1811821820² = 6565396614856224800, which contains 22 as substring.

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, 296951 + ... + 302990.

It is an arithmetic number, because the mean of its divisors is an integer number (159584572).

Almost surely, 2^1811821820 is an apocalyptic number.

1811821820 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1811821820 is an abundant number, since it is smaller than the sum of its proper divisors (2018207908).

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

1811821820 is a wasteful number, since it uses less digits than its factorization.

1811821820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 600101 (or 600099 counting only the distinct ones).

The product of its (nonzero) digits is 2048, while the sum is 32.

The square root of 1811821820 is about 42565.5003494614. The cubic root of 1811821820 is about 1219.0976531070.

The spelling of 1811821820 in words is "one billion, eight hundred eleven million, eight hundred twenty-one thousand, eight hundred twenty".