21038556820 has 12 divisors (see below), whose sum is σ = 44180969364. Its totient is φ = 8415422720.

The previous prime is 21038556743. The next prime is 21038556827. The reversal of 21038556820 is 2865583012.

It can be written as a sum of positive squares in 2 ways, for example, as 14211500944 + 6827055876 = 119212^2 + 82626^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21038556827) 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, 525963901 + ... + 525963940.

It is an arithmetic number, because the mean of its divisors is an integer number (3681747447).

Almost surely, 2^21038556820 is an apocalyptic number.

21038556820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21038556820 is an abundant number, since it is smaller than the sum of its proper divisors (23142412544).

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

21038556820 is a wasteful number, since it uses less digits than its factorization.

21038556820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1051927850 (or 1051927848 counting only the distinct ones).

The product of its (nonzero) digits is 115200, while the sum is 40.

The spelling of 21038556820 in words is "twenty-one billion, thirty-eight million, five hundred fifty-six thousand, eight hundred twenty".