20556721408 has 36 divisors (see below), whose sum is σ = 42817205088. Its totient is φ = 9831472640.

The previous prime is 20556721403. The next prime is 20556721417. The reversal of 20556721408 is 80412765502.

It is a super-2 number, since 2×20556721408² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20556721403) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1739758 + ... + 1751533.

It is an arithmetic number, because the mean of its divisors is an integer number (1189366808).

Almost surely, 2^20556721408 is an apocalyptic number.

It is an amenable number.

20556721408 is an abundant number, since it is smaller than the sum of its proper divisors (22260483680).

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

20556721408 is an equidigital number, since it uses as much as digits as its factorization.

20556721408 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3491330 (or 3491316 counting only the distinct ones).

The product of its (nonzero) digits is 134400, while the sum is 40.

The spelling of 20556721408 in words is "twenty billion, five hundred fifty-six million, seven hundred twenty-one thousand, four hundred eight".