21564090128 has 240 divisors, whose sum is σ = 53953153920. Its totient is φ = 8285663232.

The previous prime is 21564090073. The next prime is 21564090173. The reversal of 21564090128 is 82109046512.

It is a Harshad number since it is a multiple of its sum of digits (38).

It is a junction number, because it is equal to n+sod(n) for n = 21564090091 and 21564090100.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 38714426 + ... + 38714982.

It is an arithmetic number, because the mean of its divisors is an integer number (224804808).

Almost surely, 2^21564090128 is an apocalyptic number.

21564090128 is a gapful number since it is divisible by the number (28) 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 21564090128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26976576960).

21564090128 is an abundant number, since it is smaller than the sum of its proper divisors (32389063792).

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

21564090128 is a wasteful number, since it uses less digits than its factorization.

21564090128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 734 (or 721 counting only the distinct ones).

The product of its (nonzero) digits is 34560, while the sum is 38.

The spelling of 21564090128 in words is "twenty-one billion, five hundred sixty-four million, ninety thousand, one hundred twenty-eight".