820400020 has 48 divisors (see below), whose sum is σ = 1886246208. Its totient is φ = 297250560.

The previous prime is 820400017. The next prime is 820400051. The reversal of 820400020 is 20004028.

820400020 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a junction number, because it is equal to n+sod(n) for n = 820399967 and 820400003.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 55672 + ... + 68848.

It is an arithmetic number, because the mean of its divisors is an integer number (39296796).

Almost surely, 2^820400020 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 820400020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (943123104).

820400020 is an abundant number, since it is smaller than the sum of its proper divisors (1065846188).

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

820400020 is a wasteful number, since it uses less digits than its factorization.

820400020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13480 (or 13478 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 16.

The square root of 820400020 is about 28642.6259271038. The cubic root of 820400020 is about 936.1423387034.

Adding to 820400020 its reverse (20004028), we get a palindrome (840404048).

The spelling of 820400020 in words is "eight hundred twenty million, four hundred thousand, twenty".