21566620020 has 192 divisors, whose sum is σ = 68313047040. Its totient is φ = 5036428800.

The previous prime is 21566620007. The next prime is 21566620063. The reversal of 21566620020 is 2002666512.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a self number, because there is not a number n which added to its sum of digits gives 21566620020.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 4683039 + ... + 4687641.

It is an arithmetic number, because the mean of its divisors is an integer number (355797120).

Almost surely, 2^21566620020 is an apocalyptic number.

21566620020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21566620020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34156523520).

21566620020 is an abundant number, since it is smaller than the sum of its proper divisors (46746427020).

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

21566620020 is a wasteful number, since it uses less digits than its factorization.

21566620020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4886 (or 4884 counting only the distinct ones).

The product of its (nonzero) digits is 8640, while the sum is 30.

The spelling of 21566620020 in words is "twenty-one billion, five hundred sixty-six million, six hundred twenty thousand, twenty".