820404473805 has 54 divisors (see below), whose sum is σ = 1654289069706. Its totient is φ = 375022601856.

The previous prime is 820404473797. The next prime is 820404473821. The reversal of 820404473805 is 508374404028.

It is a happy number.

It can be written as a sum of positive squares in 3 ways, for example, as 204573480804 + 615830993001 = 452298^2 + 784749^2 .

It is not a de Polignac number, because 820404473805 - 2³ = 820404473797 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 53 ways as a sum of consecutive naturals, for example, 42522601 + ... + 42541889.

Almost surely, 2^820404473805 is an apocalyptic number.

It is an amenable number.

820404473805 is an abundant number, since it is smaller than the sum of its proper divisors (833884595901).

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

820404473805 is an frugal number, since it uses more digits than its factorization.

820404473805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 38603 (or 19304 counting only the distinct ones).

The product of its (nonzero) digits is 860160, while the sum is 45.

Multiplying 820404473805 by its sum of digits (45), we get a square (36918201321225 = 6076035²).

820404473805 divided by its sum of digits (45) gives a square (18231210529 = 135023²).

The spelling of 820404473805 in words is "eight hundred twenty billion, four hundred four million, four hundred seventy-three thousand, eight hundred five".