1821801820 has 24 divisors (see below), whose sum is σ = 3859645104. Its totient is φ = 722270976.

The previous prime is 1821801809. The next prime is 1821801841. The reversal of 1821801820 is 281081281.

It is a happy number.

It is a super-3 number, since 3×1821801820³ (a number of 29 digits) contains 333 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, 400794 + ... + 405313.

It is an arithmetic number, because the mean of its divisors is an integer number (160818546).

Almost surely, 2^1821801820 is an apocalyptic number.

1821801820 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1821801820 is an abundant number, since it is smaller than the sum of its proper divisors (2037843284).

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

1821801820 is a wasteful number, since it uses less digits than its factorization.

1821801820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 806229 (or 806227 counting only the distinct ones).

The product of its (nonzero) digits is 2048, while the sum is 31.

The square root of 1821801820 is about 42682.5704474321. The cubic root of 1821801820 is about 1221.3319279494.

The spelling of 1821801820 in words is "one billion, eight hundred twenty-one million, eight hundred one thousand, eight hundred twenty".