21056516020 has 12 divisors (see below), whose sum is σ = 44218683684. Its totient is φ = 8422606400.

The previous prime is 21056516003. The next prime is 21056516023. The reversal of 21056516020 is 2061565012.

It can be written as a sum of positive squares in 2 ways, for example, as 13080954384 + 7975561636 = 114372^2 + 89306^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21056516020.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21056516023) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 526412881 + ... + 526412920.

It is an arithmetic number, because the mean of its divisors is an integer number (3684890307).

Almost surely, 2^21056516020 is an apocalyptic number.

21056516020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21056516020 is an abundant number, since it is smaller than the sum of its proper divisors (23162167664).

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

21056516020 is a wasteful number, since it uses less digits than its factorization.

21056516020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1052825810 (or 1052825808 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 28.

The spelling of 21056516020 in words is "twenty-one billion, fifty-six million, five hundred sixteen thousand, twenty".