1811800821 has 4 divisors (see below), whose sum is σ = 2415734432. Its totient is φ = 1207867212.

The previous prime is 1811800819. The next prime is 1811800849. The reversal of 1811800821 is 1280081181.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 1811800821 - 2¹ = 1811800819 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1811800021) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 301966801 + ... + 301966806.

It is an arithmetic number, because the mean of its divisors is an integer number (603933608).

Almost surely, 2^1811800821 is an apocalyptic number.

It is an amenable number.

1811800821 is a deficient number, since it is larger than the sum of its proper divisors (603933611).

1811800821 is an equidigital number, since it uses as much as digits as its factorization.

1811800821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 603933610.

The product of its (nonzero) digits is 1024, while the sum is 30.

The square root of 1811800821 is about 42565.2536818471. The cubic root of 1811800821 is about 1219.0929433115.

The spelling of 1811800821 in words is "one billion, eight hundred eleven million, eight hundred thousand, eight hundred twenty-one".